"Without Tom pushing it, I don't think we would have had Romneycare," Romney said of Stemberg, who died earlier in the day.
Romney added, "Without Romneycare, I don't think we would have Obamacare. So, without Tom a lot of people wouldn't have health insurance."
Mitt Romney general - updated 5/19/2015
Mitt Romney has made a surprising comment about Obamacare
Mitt Romney and Evander Holyfield fight in a charity boxing event on May 15, 2015 in Salt Lake City, Utah. The event was held to raise money for 'Charity Vision' a charity that aims to restore sight to the blind and visually impaired. (Photo by George Frey/Getty Images)
Mitt Romney Visits 'The Tonight Show Starring Jimmy Fallon' at Rockefeller Center on March 25, 2015 in New York City. (Photo by Theo Wargo/NBC/Getty Images for 'The Tonight Show Starring Jimmy Fallon')
Mitt Romney is greeted by fellow Republicans at a dinner during the Republican National Committee's Annual Winter Meeting aboard the USS Midway on January 16, 2015 in San Diego, California. Romney is contemplating a possible 2016 presidential run. (Photo by Sandy Huffaker/Getty Images)
Former Massachusetts Gov. Mitt Romney addresses the crowd during a rally for Republican Senate candidate Dan Sullivan at a PenAir airplane hangar on November 3, 2014 in Anchorage, Alaska. The U.S. Senate race in Alaska between incumbent Democratic Sen. Mark Begich and Republican candidate Dan Sullivan continues to be closely contested. (Photo by David Ryder/Getty Images)
Former Massachusetts Gov. and GOP presidential candidate Mitt Romney makes his way through supporters of Iowa Republican State Senator and U.S. Senate candidate Joni Ernst on October 11, 2014 in Cedar Rapids, Iowa. Ernst and Romney met with around 300 supporters at the event, one of many in the final weeks of Ernst's campaign for a U.S. Senate seat. U.S. Representative Bruce Braley (D-IA) and Ernst are virtually tied in polling to replace the seat occupied by retiring U.S. Senator Tom Harkin (D-IA). (Photo by David Greedy/Getty Images)
Governor Charlie Baker was sworn in as the governor of Massachusetts at a ceremony inside the House Chamber at the State House on January 8, 2015. Mitt Romney greets Chris Christie after Gov. Baker's swearing in. (Photo by John Tlumacki/The Boston Globe via Getty Images)
Mitt Romney attends the New York Jets vs. Miami Dolphins game at MetLife Stadium on December 1, 2014 in East Rutherford, New Jersey. (Photo by Al Pereira/WireImage)
Former Massachusetts Gov. Mitt Romney walks to the stage during a rally for Republican Senate candidate Dan Sullivan at a PenAir airplane hangar on November 3, 2014 in Anchorage, Alaska. The U.S. Senate race in Alaska between incumbent Democratic Sen. Mark Begich and Republican candidate Dan Sullivan continues to be closely contested. (Photo by David Ryder/Getty Images)
Former Republican presidential candidate and former Massachusetts Governor Mitt Romney, delivers remarks during a 'CoMITT to the Comeback' rally for Michigan republican candidates October 2, 2014 in Livonia, Michigan. Among the Michigan candidates in attendance were U.S. Senate Candidate Terri Lynn Land, Lt. Gov. Brian Calley, Attorney General Bill Schuette, and Secretary of State Ruth Johnson. (Photo by Bill Pugliano/Getty Images)
Former Republican presidential candidate Mitt Romney speaks during a political rally for Republican candidate for Colorado Governor Bob Beauprez, at Heritage High School, in the Denver suburb of Littleton, Colo., Monday, Sept. 29, 2014. Romney criticized Colorado Democratic Gov. John Hickenlooper during a rally in which he cheered on GOP candidates for governor and Congress. (AP Photo/Brennan Linsley)
Mitt Romney, the former Republican presidential nominee, addresses a crowd of supporters while introducing New Hampshire Senate candidate Scott Brown at a farm in Stratham, N.H., Wednesday, July 2, 2014. Brown, who is facing incumbent Democrat U.S. Sen. Jeanne Shaheen, was endorsed by Romney at the event. (AP Photo/Charles Krupa)
Former GOP presidential candidate Mitt Romney greets the lunch crowd at the Varsity, Wednesday, Oct. 1, 2014, in Atlanta. Romney attended a private fundraiser for Republican candidate for Senate David Perdue earlier. Romney is the Republican man in demand. The twice-defeated White House contender is campaigning across seven states in five days this week to raise money and energy for Republican midterm candidates. (AP Photo/John Bazemore)
Ann Romney and former Governor of Massachusetts Mitt Romney attend the 3rd Annual NFL Honors at Radio City Music Hall on February 1, 2014 in New York City. (Photo by Slaven Vlasic/Getty Images)
LAS VEGAS, NV - DECEMBER 08: Former Republican presidential candiate and Massachusetts Gov. Mitt Romney sits ringside fro the Patrick Hyland and Javier Fortuna WBA interim featherweight title fight at the MGM Grand Garden Arena on December 8, 2012 in Las Vegas, Nevada. (Photo by Al Bello/Getty Images)
Mitt Romney, the former Republican presidential nominee, kisses a supporter while campaigning for New Hampshire Senate candidate Scott Brown, right, at a farm in Stratham, N.H., Wednesday, July 2, 2014. Brown, who is facing incumbent Democrat U.S. Sen. Jeanne Shaheen, was endorsed by Romney at the event. (AP Photo/Charles Krupa)
FILE - In this Dec. 8, 2012, file photo, former Republican presidential candidate Mitt Romney, center, joined by wife Ann, right, talks with an unidentified spectator at ringside prior to a welterweight fight between Juan Manuel Marquez and Manny Pacquiao title fight in Las Vegas. Romney has emerged from nearly four months in seclusion for an interview with Fox News. Heâs also scheduled to deliver his first postelection speech this month at Washingtonâs Conservative Political Action Conference. (AP Photo/Julie Jacobson, File)
FILE - This Nov. 7, 2012 file photo shows Republican presidential candidate, former Massachusetts Gov. Mitt Romney waving to supporters at an election night rally in Boston. Romneyâs shadow looms over a GOP in disarray. Republican officials in Washington and elsewhere concede that Romneyâs immediate withdrawal from politics _ while welcome by most _ has created a leadership void, leaving the GOP rudderless and fighting with itself during what may be the most important policy debate in a generation. (AP Photo/Stephan Savoia, File)
Republican presidential candidate, former Massachusetts Gov. Mitt Romney pauses as he addresses campaign workers while visiting a campaign call center in Green Tree, Pa., Tuesday, Nov. 6, 2012. (AP Photo/Charles Dharapak)
Republican presidential candidate, former Massachusetts Gov. Mitt Romney and his wife Ann Romney emerge after they voted in Belmont, Mass., Tuesday, Nov. 6, 2012. (AP Photo/Charles Dharapak)
Republican presidential candidate, former Massachusetts Gov. Mitt Romney and wife Ann Romney vote in Belmont, Mass., Tuesday, Nov. 6, 2012. (AP Photo/Charles Dharapak)
Republican presidential candidate former Massachusetts Gov. Mitt Romney waves to a crowd gathered at a nearby parking lot after his campaign plane arrived at Moon Township Pittsburgh International Airport in Coraopolis, Pa., Tuesday, Nov. 6, 2012. (AP Photo/Charles Dharapak)
Former Republican presidential nominee Mitt Romney gets a hug from Emma Nemecek, of Mt. Vernon, Iowa, during a rally for Iowa Republican Senate candidate Joni Ernst, Friday, May 30, 2014, in Cedar Rapids, Iowa. (AP Photo/Charlie Neibergall)
Republican presidential candidate Mitt Romney arrives on stage on election night November 7, 2012 in Boston, Massachusetts, moments before conceding defeat to US President Barack Obama in the 2012 US presidential election. AFP PHOTO/EMMANUEL DUNAND (Photo credit should read EMMANUEL DUNAND/AFP/Getty Images)
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Political observers widely found that to be an eyebrow-raising comment. During the 2012 election, Romney criticized President Barack Obama's signature healthcare bill, which is one of the most reviled pieces of legislation among conservative activists.
But as Romney's critics pointed out at the time, he pushed for a relatively similar healthcare overhaul in his state, including the controversial insurance mandate.