Romney, who once hoped to be accepting the GOP presidential nomination this week, lauded his former rival in prime-time remarks that prompted almost deafening cheers inside the convention hall.
"We need change all right - change from a liberal Washington to a conservative Washington," Romney said. "We have a prescription for every American who wants change in Washington - throw out the big government liberals and elect John McCain and [vice presidential nominee] Sarah Palin."
Romney - who told CNN in January that McCain couldn't change Washington because he was a "creature of Washington" and an advocate for "liberal causes" - railed against liberals, deriding them 14 times in his 11-minute speech.
He painted Democrats as the party of European ideas like higher taxes, bigger government and less trade. Republicans, he said, want an American solution.
"It is to rein in government spending and to lower taxes, for taking a weed-whacker to excessive regulation and mandates, for putting a stop to tort windfalls, and to stand up to the Tyrannosaurus appetite of government unions," Romney said.
It was a bittersweet speech for Romney, who spent $45 million of his own fortune seeking the White House. He showed no remorse.
"Republicans, led by John McCain and [vice presidential nominee] Sarah Palin, will fight to preserve the values that have preserved the nation," Romney cheered.
Interrupted twice by a chant of "USA, USA," and "go, Mitt, go," - the latter started by the Utah delegation - Romney played up his role as McCain's loyal soldier.
The former head of the 2002 Winter Olympics in Salt Lake City, who parlayed that role into the Massachusetts governor's office, failed in his presidential bid, but got a piece of the national stage on Wednesday.
But he also diverted from his prepared remarks on the teleprompter to assuage a supportive crowd. "We have deep respect for all of you," Romney said. "My dear friends, we sure love you."
He had no love for Democrats.
"It's time to stop the spread of government dependency to fight it like the poison it is!" Romney said, donning his staple blue tie. "It's time for the party of big ideas, not the party of Big Brother."
He charged Democrats want to enlarge government and raise taxes, put more people on Medicaid, and "grow the ranks of those who pay no taxes."
Massachusetts Democratic Party Chairman John Walsh responded in kind.
"Watching Mitt Romney's speech fall so flat tonight reminded us all why he lost so many primaries during the year," Walsh said. "Even though the Olympics just ended, it is amazing how Mitt still gets top scores in the Olympic flip-flopping event."
Shortly after his speech, Romney made his first stop to the Utah delegation, receiving a hero's welcome.
"You make us so proud," GOP 3rd District candidate Jason Chaffetz told him.
"You're a great American," chimed in Lt. Gov. Gary Herbert.
Romney revived some of his own campaign trail stump speech during his address Wednesday night.
"Just like you, there has never been a day when I was not proud to be an American," Romney said. "We inherited the greatest nation in the history of the earth. It is our burden and privilege to preserve it, to renew its spirit so that its noble past is prologue to its glorious future."
