Trump endorses Romney - CNN.com News of Donald Trump's endorsement of Mitt Romney comes two days before the Nevada caucuses. NEW: Trump calls Romney tough and smart, and praises his criticism of China NEW: Romney concedes that Trump is a more successful businessman NEW: Santorum agrees with Gingrich that Florida delegates should be proportional (CNN) -- Celebrity business magnate Donald Trump endorsed Mitt Romney for president Thursday, telling reporters he will not mount an independent campaign if Romney is the Republican nominee. Trump, who has repeatedly flirted with the possibility of his own White House bid, revealed his decision in Las Vegas two days before Nevada's Saturday caucuses. "It's my honor, real honor, to endorse Mitt Romney," Trump said, with Romney and his wife standing nearby. Calling Romney "tough" and "smart," Trump said, "he's not going to continue to allow bad things to happen to this country." Romney responded by praising Trump for "an extraordinary ability to understand how our economy works and to create jobs" and for being "one of the few who has stood up to say China is cheating" in international trade. It was unclear whether Trump's decision will have any impact on the Republican race. A Pew survey last month found that 64% of definite and likely GOP voters said an endorsement from the reality television star would make no difference to them. In the survey, 13% said it would make them more likely to back a candidate, while 20% said it would actually make them less likely. "Endorsements rarely sway voters," Republican strategist Alex Castellanos said. But "the Trump endorsement undermines (Newt) Gingrich's argument that it is just the Washington establishment that is out to stop him and nominate Romney. Trump is the ultimate outsider. Trump was not always so positive regarding Romney's record. During an interview on CNN's "State of the Union" in April, Trump criticized Romney for eliminating jobs while in the private sector. He'd buy companies. He'd close companies. He'd get rid of jobs," Trump told CNN Chief Political Correspondent Candy Crowley. I've built a great company. My net worth is many many times Mitt Romney. Perhaps in reference to Trump's earlier comments, Romney said Thursday after thanking Trump for the endorsement, "I spent my life in the private sector, not quite as successful as this guy but successful nonetheless." Poll: Romney's big lead in Nevada "We have a safety net" for the very poor, Romney told CNN's Soledad O'Brien on Wednesday. Romney later insisted that his words were taken out of context and reiterated the full context of the quote, which was meant to stress his focus on the middle class. Gingrich hammers Romney over 'poor' comment Romney is "reinforcing the image of the national party that is elite (and) out of touch," said Mark McKinnon, a former campaign adviser to George W. Bush and John McCain. Gingrich, the former House speaker, has blasted Romney for the remark over the past two days, declaring Wednesday that he is "fed up with politicians in either party dividing Americans against each other." On Thursday, Gingrich said that "we should care about the very poor -- unlike Governor Romney. But I believe that we should care differently than Barack Obama. Both Governor Romney and Barack Obama seem to believe that a 'safety net' is all the poor need. I don't believe that. What the poor need is a trampoline so they can spring up and quit being poor. Gingrich press secretary fights off Trump questions The Gallup daily tracking poll had Gingrich ahead of Romney after the former speaker won the January 21 South Carolina primary. Romney won the primary with 46% of the vote, compared with 32% for Gingrich, 13% for Rick Santorum and 7% for Ron Paul, according to the Florida Department of State. Zakaria: Why I can't wait for the Republican convention Gingrich's campaign asked the Republican Party on Thursday to allocate the 50 Florida delegates on a proportional basis, rather than the winner-take-all format that gave them to Romney. In a letter to the Republican National Committee, the Gingrich campaign argued that an RNC rule says early primaries and caucuses must award delegates proportionally. However, party rules say the issue can be addressed only at the August nominating convention in Tampa, Florida. Santorum also has expressed support for Florida to change its system, but the Florida Republican Party chairman, Lenny Curry, said in a statement Thursday that won't happen. "Florida was winner-take-all before election day, we were winner-take-all on election day, we will remain winner-take-all," Curry's statement said, adding: "It is a shame when the loser of a contest agrees to the rules before, then cries foul after losing." CNN's Tom Cohen, Jim Acosta, Paul Steinhauser and Alyssa McLendon contributed to this report.