ST. PETERSBURG, Fla. - Never once mentioning President George W. Bush by name, or acknowledging that the former president endorsed his candidacy Tuesday, Mitt Romney spent the morning in Florida railing against President Obama for doing too little to solve the debt crisis he inherited from his "predecessor."

"I love this country, as I know you do, but I'm concerned about this country," Romney said on his first public campaign swing through the battleground state since winning the primary here in January. "I'm concerned about the debt. I'm concerned about the spending.

"I find it incomprehensible that a president could come to office and call his predecessor's record irresponsible and unpatriotic and then do almost nothing to fix it."

Bush told ABC News Tuesday, as an elevator door closed, "I'm for Mitt Romney," joining the rest of his family in backing the presumptive GOP nominee. But the Romney campaign, and now the candidate, has since remained mum on the endorsement.

Bush's popularity has risen since leaving office, yet more people still view him unfavorably and blame him for the economic collapse, according to polling.

The Obama campaign published a statement on Bush's endorsement of Romney before the Romney campaign did.

Romney today mentioned Obama's "predecessor," Bush, no fewer than five times in talking about the debt crisis.

"[Obama] was very critical of his predecessor for the debts his predecessor put in place," Romney said. "And sure it's true you can't blame one party or the other for all the debts this country has, because both parties in my opinion have spent too much and borrowed too much when they were in power. But he was very critical of his predecessor because the predecessor put together $4 trillion of debt over eight years. This president however - oh, by the way, he said that doing that was unpatriotic, irresponsible and unpatriotic. And he said he would cut the debt in half if he became president.

"Instead he doubled it, alright, he doubled it," Romney added.

The National Debt shot up nearly $5 trillion during the Bush administration, and has increased by about the same amount under the Obama administration, according to the Treasury Department. The debt, however, was greatly affected by the onset of the recession, which began during the Bush administration.

"It is not at all what he promised," Romney said as the crowd, giving him standing ovations throughout the speech, roared in applause. "This presidency has been a disappointment and the people who have been hurt by this disappointment are the American people and that's why we're going to get him out of office come November."

Lis Smith, a campaign spokeswoman for the Obama, said in a statement that Romney "continued to make dishonest claims" about Obama and his own record.

"And Mitt Romney ignores that when President Obama took office, he was handed the largest deficit relative to the economy since the end of World War II, largely due to failed economic policies that Mitt Romney would bring back," Smith said.

"While President Obama has put forward a plan to reduce the deficit by more than $4 trillion by making responsible spending cuts and asking every American to pay their share, Mitt Romney refuses to say what spending cuts or tax increases he'd make to cover the cost of giving $5 trillion in tax breaks to the wealthiest Americans," Smith said. 

Before heading off to two private fundraisers, Romney did make a plea to the coveted independent voters who will be crucial this November.

"I can tell from this audience that you're kind of leaning my way, right, yeah?" Romney said. "But I need you to go out and talk to your friends and get them to lean this way as well. And there are a lot of people who haven't heard from us. We need to get to the college kids, for instance, and people coming out of high school, and folks that have only lived in Florida for short while and say, 'Guys, did you know there's about a half million dollars that this government has in debt and obligations on your household? And this president keeps spending more and more, and hiding from you what's going on. We've got to get this guy Romney in there so we can have a brighter future for ourselves; create jobs and have a brighter future for our kids.'"