"President Obama promised to begin to slow the rise of the oceans and to heal the planet. My promise is to help you and your family," Romney said Thursday after accepting the GOP nomination.
"Today the time has come for us to put the disappointments of the last four years behind us," Romney said, adding the "hope and change" Obama promised in his 2008 campaign "is not what America wanted; is not what America expected. It was what America deserved."
Romney was introduced by U.S. Sen. Marco Rubio of Florida, a rising star in the party who was on the short list to be Romney's running mate before Rep. Paul Ryan of Wisconsin was added to the GOP ticket.
"No matter how you feel about President Obama, this election is about your future, not his," Rubio said, conceding Obama "isn't a bad person," he's just a "bad president."
The final day of the hurricane-truncated convention included an appearance from Hollywood legend Clint Eastwood, who told delegates, "When somebody doesn't do the job, we've got to let them go."
Eastwood noted he cried when Obama was elected in 2008 but said "23 million people unemployed or underemployed is something to cry for."
"Politicians are employees of ours" and "we own this country," he said.
Acknowledging Obama was "dealt a tough hand," Bush nonetheless said the president's policies haven't worked.
"In the fourth year of your presidency, a real leader would accept responsibility for his actions, and you haven't done it," he said.
Earlier, former House Speaker Newt Gingrich, who challenged Romney for the presidential nod, appeared with his wife, Callista, to say Romney will "renew the American spirit" by channeling the legacy of Ronald Reagan.
Gingrich said it was "striking" how Jimmy Carter and Barack Obama "both took our nation down a path that in four years weakened America's confidence in itself and our hope for a better future."
"Remembering President Reagan reminds us that the choices we make matter, and this year is as important as the choice we made in 1980," Callista Gingrich said. "Governor Romney will return America to work, and to the principles that are at the core of President Reagan's legacy."
The debt clock Republicans revealed Monday at the start of the convention showed the United States racked up $8.5 billion in debt during the GOP confab.
The Democratic National Convention takes place next week in Charlotte, N.C.