PHILADELPHIA, July 27 (Reuters) - Democratic vice presidential nominee U.S. Senator Tim Kaine laid into Republican candidate Donald Trump on Wednesday, describing the billionaire as "a one-man wrecking crew" who cannot be trusted with America's future.
"Our nation, it is just too great to put it in the hands of a slick-talking, empty-promising, self-promoting, one-man wrecking crew," Kaine said in a keynote speech to the Democratic Party convention in Philadelphia.
Democratic presidential nominee Hillary Clinton chose Kaine of Virginia, as her running mate last week, opting for a partner at the Nov. 8 election who has wide experience in public service to draw a contrast with Trump who has never been elected to office.
Peppering his speech with phrases in Spanish, the bilingual Kaine said he and Clinton were "companeros de alma," or soul mates, and led chants from the crowd of "Si, se puede." ("Yes, we can.")
Kaine said Trump, a businessman and reality TV show host, was fundamentally untrustworthy.
"He never tells you how he's going to do any of the things he says he's going to do. He just says, 'believe me.' So here's the question. Do you really believe him? Donald Trump's whole career says you better not," Kaine said.
He went on to criticize the GOP nominee for refusing to release his tax returns, asking, "Hey Donald, what are you hiding?"
See more of Kaine through the years:
Senator Tim Kaine through his career
Senator Tim Kaine through his career
Democratic U.S. presidential candidate Hillary Clinton and U.S. Senator Tim Kaine (D-VA) react during a campaign rally at Ernst Community Cultural Center in Annandale, Virginia, U.S., July 14, 2016. REUTERS/Carlos Barria TPX IMAGES OF THE DAY
DATE:10/06/2001 SLUG:ME/KAINE CREDIT:TRACY A WOODWARD/TWP Candidate for VA Lt Gov. Tim Kaine at Herndon, VA., Homecoming Parade. Along parade route through the town of Herndon; Kaine (center of photo-blue shirt and jacket) shakes hands with Herndon High School student- Nick Palatiello (cq) 18 yrs old. The kids are on one of the Herndon High School floats. Original Filename: MEKAINE2.jpg ORG XMIT: M0110071405302067 (Photo by Tracy A. Woodward/The Washington Post/Getty Images)
SLUG: ME/RICHMOND The second day of the Virginia general assembly. Pictured, Lt. Governor Tim Kaine holds a press conference in the statehouse to introduce his legislative staffers and answer questions from the press. (Photo by Bill O'Leary/The Washington Post/Getty Images)
SLUG: ME/INAUG DATE: 01/14/2006 CREDIT: Bill O'Leary Governor Tim Kaine is inaugurated at the colonial statehouse in Williamsburg, VA. Pictured, the Governor elect gives a thumbs up signal to the crowd during a long ovation upon his arrival. (Photo by Bill O'Leary/The Washington Post/Getty Images)
Virginia Gov. Tim Kaine laughs at a remark by President George W. Bush about his wife's needle work while visiting the Jamestown Settlement in Jamestown, Virginia, Sunday, May 13, 2007. (Photo by Dave Bowman/Newport News Daily Press/MCT via Getty Images)
CHESTER, VA - AUGUST 21: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) (R) discusses economy with people as Virginia Gov. Tim Kaine (L) looks on during a campaign stop at John Tyler Community College August 21, 2008 in Chester, Virginia. The media have been reported that Obama will announce who is his running mate in Springfield, Illinois on Saturday. (Photo by Alex Wong/Getty Images)
DENVER - AUGUST 28: Virginia Gov. Tim Kaine walks off stage on day four of the Democratic National Convention (DNC) at Invesco Field at Mile High August 28, 2008 in Denver, Colorado. U.S. Sen. Barack Obama (D-IL) is the first African-American to be officially nominated as a candidate for U.S. president by a major party. (Photo by Win McNamee/Getty Images)
UNITED STATES - JANUARY 08: Virginia Governor Tim Kaine and President elect Barack Obama speak at a news conference at the Democratic National Committee headquarters to announce Kaine as the new chair of the DNC on January 8, 2009. (Photo By Bill Clark/Roll Call/Getty Images)
RICHMOND, VA - NOVEMBER 04: Virginia Gov. and Democratic National Committee Chairman Tim Kaine answers questions during a press conference at the State Capitol complex November 4, 2009 in Richmond, Virginia. Kaine discussed the results of yesterday's election results during the press conference. (Photo by Win McNamee/Getty Images)
WASHINGTON, DC - SEPTEMBER 30: DNC Chairman Tim Kaine (L) participates in a conference call with Rev. Regena Thomas, Director of Faith and Constituency Outreach in the Chairman's office on September 30, 2010. This was a 5:00 pm Conference call with the National Baptist Convention Leadership. (Photo by Tracy A Woodward/The Washington Post via Getty Images)
VIRGINIA BEACH, VA, JULY 13: Former Virginia Gov. Tim Kaine plays to the crowd during a campaign stop with President Barack Obama at Green Run High School in Virginia Beach, Virginia, on Friday, July 13, 2012. (Photo by Nikki Kahn/The Washington Post via Getty Images)
MCLEAN, VA - SEPTEMBER 20: Tim Kaine in encircled by media in the media room of the Capitol One Conference Center following his U.S. Senatorial debate against George Allen on Thursday, September 20, 2012, in McLean, VA. The former Virginia governor Kaine is in a heated run against Allen, another former Virginia governor, for the US Senate seat being vacated by Senator Jim Webb. In addition to being a former Virginia governor, Kaine, a Democrat , is a former mayor of Richmond and a Virginia Lt. governor. Kaine's wife, Holton, has been active in the campaign, making appearances around the state on her husband's behalf. (Photo by Jahi Chikwendiu/The Washington Post via Getty Images)
FAIRFAX, VA - SEPTEMBER 25: U.S. Senate Democratic candidate and former Virginia Gov. Tim Kaine answers reporters' questions during a news conference at the Fairfax County Fire and Rescue Station 40 September 25, 2012 in Fairfax, Virginia. The International Association of Fire Fighters union announced its endorsement of Kaine in his race against another former Virginia governor and former U.S. Senator George Allen (R-VA). (Photo by Chip Somodevilla/Getty Images)
UNITED STATES - November 6 : Former Governor of Virginia, Tim Kanie makes his acceptance speech after winning the Virginia Senate seat from Former Governor George Allen at Kaine's election night party at the Richmond Marriott on November 6, 2012. (Photo By Douglas Graham/CQ Roll Call)
WASHINGTON, DC - JANUARY 19: (L-R) Maryland Governor Martin O'Malley, Anne Holton, and Senator Tim Kaine (D-VA) attend the Inaugural Youth Ball hosted by OurTime.org at Donald W. Reynolds Center on January 19, 2013 in Washington, United States. (Photo by Michael Kovac/FilmMagic)
WASHINGTON, DC - JULY 31: Junior Senator Tim Kaine (D-VA) looks up to think for a moment during a staff meeting in his office on Capitol Hill Wednesday, July 31, 2013. (Photo by Melina Mara/The Washington Post via Getty Images)
US Senator Tim Kaine,D-Virginia, listens to witnesses June 5, 2014 during hearings held by the US Senate Foreign Relations Committee On Capitol Hill in Washington, DC. The committee is hearing testimony on 'Development in Ukraine.' AFP PHOTO / Karen BEIER (Photo credit should read KAREN BLEIER/AFP/Getty Images)
UNITED STATES - JUNE 9: Sen. Tim Kaine, D-Va., speaks with a reporter as he arrives for the Senate Democrats' policy lunch in the Capitol on Tuesday, June 9, 2015. (Photo By Bill Clark/CQ Roll Call)
MEET THE PRESS -- Pictured: (l-r) Sen. Tim Kaine (D-VA) appears in pre taped interview on 'Meet the Press' in Washington, D.C., Friday June 24, 2016. (Photo by: William B. Plowman/NBC/NBC NewsWire via Getty Images)
US Democratic Presidential candidate Hillary Clinton and US Senator Tim Kaine, Democrat of Virginia, wave during a campaign rally at Ernst Community Cultural Center in Annandale, Virginia, on July 14, 2016. / AFP / SAUL LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)
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Senior Democrats and former national security figures lined up in Philadelphia on Wednesday to describe Trump as unable to steer America through the dangerous waters of today's world.
The Republican on Wednesday gave his critics fresh fodder for attack with remarks about Russia that the Clinton campaign said posed a possible national security threat.
Grabbing the spotlight at a news conference in Miami, Trump urged Russia to find and release tens of thousands of emails that Clinton did not hand over to U.S. officials as part of a probe into her use of a private email system while she was secretary of state. Clinton has said those emails were private.
In an earlier speech in Philadelphia, U.S. Vice President Joe Biden said Trump was an opportunist who has no clue about how to make America great or help working families.
Drawing chants of "Not a clue" from the floor of the convention, Biden took Trump to task for his trademark reality TV slogan, "You're fired."
"He's trying to tell us he cares about the middle class. Give me a break. That's a bunch of malarkey!" Biden shouted to cheers in the Wells Fargo Center.
Trump has hammered Clinton as untrustworthy and cast America as a place where security threats abound and law and order are breaking down.
He has proposed deeply controversial measures such as temporarily banning Muslims from entering the country and building a wall on the border with Mexico to stop illegal immigrants.
Trump got a boost in opinion polls from his nomination at the Republican convention last week. He had a 2-point lead over Clinton in a Reuters/Ipsos opinion poll released on Tuesday, the firsttime he has been ahead since early May.
(Additional reporting by Amy Tennery, Emily Stephenson, Jonathan Allen, Susan Heavey, Doina Chiacu, Steve Holland and Frances Kerry; Writing by Frances Kerry and Alistair Bell; Editing by Peter Cooney and Howard Goller; Additional reporting by AOL.com)