In an abrupt about-face in strategy, Marco Rubio on Wednesday night attacked Donald Trump on policy by name from the stump, drawing the battle lines for a certain showdown with the GOP front-runner on the eve of Thursday's debate.
At an energetic rally in Houston, Rubio targeted Trump on Obamacare and Israel, charging Trump "thinks parts of Obamacare are pretty good" and that he's refused to come to Israel's defense.
"The front-runner in this race, Donald Trump, has said he's not going to take sides on Israel versus the Palestinians because he wants to be an honest broker," Rubio said. "Well, there is no such thing as an honest broker in that. Because the Palestinian Authority, which has strong links to terror, they teach little kids that it's a glorious thing to kill Jews."
Rubio also alluded to Trump's claim that he can leave foreign policy details murky because he'll simply bring in the best advisers, telling the crowd, "We cannot have a commander-in-chief that is not ready the first day in office."
"You can't just say, the way some people in this race have said — you'll probably know what I'm talking about in a moment — you can't just say, 'Well, when I get there I'll hire the smartest people and they're going to tell me what to do,'" Rubio said.
See images of Marco Rubio on the campaign trail:
Marco Rubio on the campaign trail
In shift, Marco Rubio attacks Donald Trump by name head of debate
IN FLIGHT - FEBRUARY 10: Republican presidential candidate Sen. Marco Rubio (R-FL) talks with reporters on his charter flight from Manchester-Boston Regional Airport February 10, 2016 en route to Spartanburg, South Carolina. Rubio placed fifth in the New Hampshire primary, behind fellow GOP candidates Jeb Bush, John Kasich, Sen. Ted Cruz (R-TX) and Donald Trump, who swept away the competition with 35-percent of the vote. (Photo by Chip Somodevilla/Getty Images)
MT PLEASANT, SC - JANUARY 13: Republican presidential candidate Sen. Marco Rubio (R-FL) greets guests during a campaign rally at the Water Dog Grill on January 13, 2016 in Mount Pleasant, South Carolina. Tomorrow Rubio will join other candidates seeking the Republican nomination for president for a debate at the North Charleston Coliseum and Performing Arts Center in North Charleston, S.C.. (Photo by Scott Olson/Getty Images)
Senator Marco Rubio, a Republican from Florida and 2016 presidential candidate, waits to speak during a town hall meeting at the Maytag Innovation Center in Newton, Iowa, U.S., on Wednesday, Dec. 30, 2015. Rubio found himself under siege on two fronts Tuesday over his attendance record in the U.S. Senate as the Florida lawmaker embarked on a swing through snowy Iowa. Photographer: Scott Morgan/Bloomberg via Getty Images
MIAMI BEACH, FL - NOVEMBER 15: Republican presidential candidate Sen. Marco Rubio (R-FL) greets people before speaking during a community rally for 'Never Again' which was bringing attention to what the organizers say is a rise in worldwide anti-Semitism and the campaign against Israel's right to exist on November 15, 2015 in Miami Beach, Florida. Rubio continues to campaign for the Republican party's nomination. (Photo by Joe Raedle/Getty Images)
CEDAR RAPIDS, IA - NOVEMBER 21: Republican presidential candidate Sen. Marco Rubio (R-FL) speaks to guests during a town hall meeting on November 21, 2015 in Cedar Rapids, Iowa. Yesterday Rubio participated in the Presidential Family Forum in Des Moines with six of his Republican rivals for the nomination. Rubio has several campaign stops scheduled in the state today. (Photo by Scott Olson/Getty Images)
Republican presidential candidate Marco Rubio speaks at the Wall Street Journal CEO Council meetings in Washington, DC, November 16, 2015. AFP PHOTO / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
ORLANDO, FL - NOVEMBER 12: Sen. Marco Rubio (R-FL) speaks at the Sunshine Summit opening dinner at Disney's Contemporary Resort on November 12, 2015 in Orlando, Florida.The dinner is the kick-off of a three-day event that will draw thousands of Republicans, mostly to hear live speeches from all the GOP presidential candidates on Friday and Saturday. (Photo by Tom Benitez - Pool/Getty Images)
ORLANDO, FL - NOVEMBER 13: Republican presidential candidate Sen. Marco Rubio (R-FL) speaks during the Sunshine Summit conference being held at the Rosen Shingle Creek on November 13, 2015 in Orlando, Florida. The summit brought Republican presidential candidates in front of the Republican voters. (Photo by Joe Raedle/Getty Images)
Senator Marco Rubio, a Republican from Florida and 2016 presidential candidate, speaks during a campaign rally at the Country Springs Hotel in Pewaukee, Wisconsin, U.S., on Monday, Nov. 9, 2015. Rubio will appear at Tuesday's Republican presidential debate in Milwaukee. Photographer: Daniel Acker/Bloomberg via Getty Images
CONCORD, NH - NOVEMBER 05: Republican Presidential candidate Marco Rubio (R-FL) files paperwork for the New Hampshire primary at the State House on November 5, 2015 in Concord, New Hampshire. Each candidate must file paperwork to be on the New Hampshire primary ballot, which will be held February 9, 2016. (Photo by Scott Eisen/Getty Images)
Republican Presidential hopeful Marco Rubio leaves the New Hampshire State House after filing for the state ballot November 5, 2015 in Concord, New Hampshire. AFP PHOTO/DON EMMERT (Photo credit should read DON EMMERT/AFP/Getty Images)
MANCHESTER, NH - NOVEMBER 4: Republican Presidential candidate Marco Rubio (R-FL) participates in a round table discussion at Saint Anselm College in Manchester, New Hampshire. Rubio is looking for a bump in the polls following a strong outing in the last debate. (Photo by Darren McCollester/Getty Images)
GREENVILLE, SC - SEPTEMBER 18: Sen. Marco Rubio (R-FL) speaks to voters at the Heritage Action Presidential Candidate Forum September 18, 2015 in Greenville, South Carolina. Eleven republican candidates each had twenty five minutes to talk to voters Friday at the Bons Secours Wellness arena in the upstate of South Carolina. (Photo by Sean Rayford/Getty Images)
NEW YORK, NY - OCTOBER 06: Republican presidential candidate, Sen. Marco Rubio (R-FL) speaks at Civic Hall about the 'sharing economy' on October 6, 2015 in New York City. Rubio, who has been experiencing a slight uptick in the polls after strong debate performances, has a second book out in paperback this Tuesday called American Dream: Restoring Economic Opportunity for Everyone. (Photo by Spencer Platt/Getty Images)
UNITED STATES - AUGUST 26: GOP Presidential candidate Sen. Marco Rubio, R-Fla., holds a town hall meeting in Londonderry, N.H., on Wednesday, Aug. 26, 2015. (Photo By Bill Clark/CQ Roll Call)
DES MOINES, IA - AUGUST 18: Republican presidential candidate and U.S. Sen. Marco Rubio (L) (R-FL) mans the grill with U.S. Rep. David Young (R) (R-IA) at the Iowa Pork Producers Pork Tent during the Iowa State Fair on August 18, 2015 in Des Moines, Iowa. Presidential candidates are addressing attendees at the Iowa State Fair on the Des Moines Register Presidential Soapbox stage and touring the fairgrounds. The State Fair runs through August 23. (Photo by Justin Sullivan/Getty Images)
UNITED STATES - August 17: Republican presidential candidate Sen. Marco Rubio, R-Fla., greets supporters during a Family Night event at Dean Park in Ankeny, Iowa, Monday, August 17, 2015. (Photo By Al Drago/CQ Roll Call)
NEW YORK, NY - AUGUST 14: Marco Rubio gives speach for the Foreign Policy Initiative at 3 West Club on August 14, 2015 in New York City. (Photo by Steve Sands/WireImage)
CLEVELAND, OH - AUGUST 06: Republican presidential candidate Sen. Marco Rubio (R-FL) participates in the first prime-time presidential debate hosted by FOX News and Facebook at the Quicken Loans Arena August 6, 2015 in Cleveland, Ohio. The top-ten GOP candidates were selected to participate in the debate based on their rank in an average of the five most recent national political polls. (Photo by Chip Somodevilla/Getty Images)
CLEVELAND, OH - AUGUST 05: Republican presidential candidate Sen. Marco Rubio (R-FL) greets guests gathered for a campaign event at Town Hall on August 5, 2015 in Cleveland, Ohio. Rubio is in Cleveland to participate in the Fox News GOP presidential candidate debate scheduled to take place tomorrow evening. The top ten polling Republican candidates were chosen to participate in the debate. (Photo by Scott Olson/Getty Images)
Senator Marco Rubio, a Republican from Florida and 2016 Republican presidential candidate, smiles while speaking during a rally at Town Hall restaurant ahead of the Fox News Republican Presidential Primary Debate in Cleveland, Ohio, U.S., on Wednesday, Aug. 5, 2015. Rubio will appear on stage with 9 other presidential candidates for the first Republican presidential debate tomorrow evening while former Texas Governor Rick Perry, former Pennsylvania Senator Rick Santorum, and Louisiana Governor Bobby Jindal didn't make the cut. Photographer: Andrew Harrer/Bloomberg via Getty Images
Senator Marco Rubio, a Republican from Florida and 2016 presidential candidate, speaks during the Faith and Freedom Coalition's 'Road to Majority' legislative luncheon in Washington, D.C., U.S., on Thursday, June 18, 2015. The annual Faith & Freedom Coalition Policy Conference gives top-tier presidential contenders as well as long shots a chance to compete for the large evangelical Christian base in the crowded Republican primary contest. Photographer: Andrew Harrer/Bloomberg via Getty Images
BOONE, IA - JUNE 06: Republican presidential hopeful U.S. Sen. Marco Rubio (R-FL) waits his turn to speak at a Roast and Ride event hosted by freshman Senator Joni Ernst (R-IA) on June 6, 2015 in Boone, Iowa. Ernst is hoping the event, which featured a motorcycle tour, a pig roast, and speeches from several 2016 presidential hopefuls, becomes an Iowa Republican tradition. (Photo by Scott Olson/Getty Images)
GREENVILLE, SC - MAY 09: Republican Presidential candidate U.S. Sen. Marco Rubio (R-FL) greets supporters at the Freedom Summit on May 9, 2015 in Greenville, South Carolina. Rubio joined eleven other potential candidates in addressing the event hosted by conservative group Citizens United. (Photo by Richard Ellis/Getty Images)
NASHUA, NH - APRIL 17: Republican presidential candidate Sen. Marco Rubio (R-FL) speaks at the First in the Nation Republican Leadership Summit April 17, 2015 in Nashua, New Hampshire. The Summit brought together local and national Republicans and was attended by all the Republicans candidates as well as those eyeing a run for the nomination. (Photo by Darren McCollester/Getty Images)
MIAMI, FL - APRIL 13: Republican Senator Marco Rubio of Florida makes a formal announcement that he is entering the 2016 Presidential race at the Freedom Tower on April 13, 2015 in Miami, Florida. (Photos by Charles Ommanney for the Washington Post)
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"The smartest people are already there. They're already telling the president what he should be doing. He's ignoring it. You deserve to know exactly what the next commander-in-chief is going to do," Rubio said.
Rubio's efforts to dismantle parts of Obamacare and his experience on foreign policy in comparison to the rest of the field are key selling points in his pitch to voters, and it appears they'll become flashpoints in his clash with Trump.
On Wednesday night, Rubio's communications team took the fight to Trump off-stage as well, with spokesman Joe Pounder suggesting Trump is complicit in the same "dirty tricks" he and Rubio have been attacking the Ted Cruz campaign for over the past few weeks.
Pounder called on Trump to repudiate a robocall reportedly telling voters in Vermont and Montana to not vote for "a Cuban, vote for Donald Trump."
"This is the lowest form of campaigning, and is the exact same type of dirty tricks Donald Trump has been decrying for weeks now," Pounder said.
The decision to take on Trump is a notable shift from just hours earlier, when Rubio was pressed on the "Today" show Wednesday morning about why he had, for weeks now, avoided a direct confrontation with the GOP front-runner.
"I didn't run for office to tear up other Republicans," Rubio said, adding that he had only been attacking Cruz because "I'm responding to Ted Cruz," who has been clashing with Rubio for weeks on immigration reform and other policy issues.
"If I'm attacked, I'm going to respond and set the record straight," Rubio said.
But Trump didn't unleash the first attack — speaking after Rubio on the Today show, Trump said of Cruz: "So far, he's been very nice and I've been very nice to him." But Trump warned "that could change."
And Rubio's decision to take aim at Trump Wednesday is all but certain to ensure that does change, and the two will likely clash on the debate stage Thursday.
It's the final GOP debate before voters head to the polls for the Super Tuesday primaries. Although Trump holds a lead in most Super Tuesday states for which there's reliable public polling, Rubio's been executing a carefully calibrated strategy to gather delegates where he can carve out support in states that award them proportionally.
Up until now, that strategy saw Rubio largely training his fire on Cruz, with whom he's been competing to emerge as the alternative to Trump.
But on Wednesday, Rubio campaign manager Terry Sullivan said in a fundraising email that "the race looks even more like a two-man race now than it did this past weekend in South Carolina." Rubio finished second behind Trump in Tuesday's Nevada caucuses.
And Rubio's attacks on Wednesday night are further evidence that the campaign sees Cruz as a waning threat and Trump a necessary target — although whether Rubio can survive the clash remains to be seen. Every candidate that's attempted to take Trump down has so far fared the worse for it, seeing their support in the polls drop precipitously after Trump hits back.
Adding to the stakes for Thursday night's debate is the fact that last time Rubio came under heavy fire from an opponent on the debate stage — when Chris Christie hammered him as "robotic" during the debate before the New Hampshire primary — Rubio folded in a performance so disappointing it cost him at the polls.