By Steve Holland
TAMPA, Florida (Reuters) - Newt Gingrich felt the sharp boot of Mitt Romney during a bitter Republican presidential primary battle, but he buried old bones and united behind his former rival on Thursday, albeit through a tribute to Ronald Reagan.
Gingrich and his wife, Callista, standing side by side on stage at the Republican National Convention, hailed Romney in the name of Reagan, the late president who is considered a hero to conservatives.
"Governor Romney will return Americans to work and to the principles that are the core of President Reagan's legacy," Callista said.
"Now each of us must commit ourselves in the tradition of Ronald Reagan to come together," said Newt, a former speaker of the U.S. House of Representatives who sharply criticized Romney during the Republican primary season as being too moderate.
The better-funded Romney and his allies launched a series of attack television ads that lampooned Gingrich for ethical violations from his time in Washington. The attacks helped prevent Gingrich from winning the Iowa caucuses in January.
On Thursday, Gingrich issued a withering attack against President Barack Obama for issuing a directive in July that allowed states to opt out of a work requirement under a welfare-to-work law.
Democrats vehemently deny Obama "gutted" the welfare law, and fact-checkers have declared that Romney television ads attacking Obama for the change are wrong.
Gingrich leaped into the fray regardless.
"Obama's waiving of the work requirement in welfare reform is just one example of his direct repudiation of President Reagan's values," he said. "Obama's proud of what he's done... but he should be ashamed for putting politics above people."
(Editing by Alistair Bell and Leslie Adler)