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TAMPA (CBSMiami/AP) — Campaigning in the crucial battleground state of Florida, Donald Trump bashed both Democrats and Republicans alike, from Hillary Clinton to former Republican presidential nominee Mitt Romney on the right.

Addressing a crowd of thousands at the Tampa Convention Center Saturday, Trump tore into "Crooked Hillary," as he calls his likely general election opponent, for the State Department email controversy and called Romney a "stone, cold loser" for not backing him as the presumptive Republican nominee.

Trump said the Republican Party "has got to get their act together, come together to win" and slammed GOP senate candidates who are not backing his run for president.

He spoke confidently of his own ability to win the presidency, but warned that down-ballot races for the House and Senate could be at risk if Republicans don't rally behind his campaign.

"The Republican party has to be tough and smart," he said. "If not, I'm gonna win but a lot of other people are not."

Trump was introduced by Florida's top Republicans, Gov. Rick Scott and Attorney General Pam Bondi.

"Donald Trump is hopeful," said Scott, whose support of Trump has generated running mate speculation. "The opposite of hopeful is Hillary Clinton."

Trump, at one point, asked the crowd to shout out names of potential running mates. House Speaker Newt Gingrich, Alabama Sen. Jeff Sessions and Condoleezza Rice, who served as secretary of state in the George W. Bush administration, were among the names he repeated.

"This is fun," bellowed Trump. "We have a lot of good people."

Toward the end of his speech, Trump supporters broke into a chorus of "Happy Birthday." He turns 70-years old on June 14.

As his supporters began singing, Trump laughed and said "I don't want to hear about it."

He said he's "very torn" about the birthday, but added: "I feel like I'm 35. That's the good news."

The Tampa rally is Trump's second since the end of the primary season. He is scheduled to hold another rally later Saturday in Pittsburgh.

(TM and © Copyright 2016 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)