Republicans formally nominated Mitt Romney on Tuesday to challenge President Barack Obama for the White House, kicking off their storm-delayed convention with a barrage of sharp attacks on Obama's economic leadership.
The nomination sets up a two-month dash to the November 6 election, with polls showing Romney running even or slightly behind the Democratic president.
Finally opening the festivities after a storm threat delayed the convention by a day, Republicans condemned Obama's economic record and reminded voters of the country's stubbornly high unemployment rate and ballooning budget deficit.
Reince Priebus, chairman of the Republican National Committee, warned that re-electing Obama would mean "four more years of failure."
"We have a message for America: Elect Mitt Romney and Paul Ryan and they'll get America working again," he said to loud cheers. "We must send America's comeback team to Washington."
The first night will be capped by prime-time speeches by Romney's wife, Ann, and New Jersey Governor Chris Christie.
Romney, who had originally planned to stay out of the spotlight until Thursday night when he accepts his party's nomination, made an early appearance in the Florida host city to be on hand for his wife's turn at the podium.
Republicans hope to make an aggressive argument to voters to replace Obama while being careful to avoid the appearance of unseemly celebration as New Orleans and swathes of the Gulf Coast were under threat from Hurricane Isaac.
Romney is struggling to overcome a "likability gap" with the president and refute Democrats' efforts to paint him as a job-killing former private equity executive who is out of touch with middle America.
Before the roll call of the states to nominate Romney, chanting supporters of libertarian congressman Ron Paul of Texas briefly disrupted the convention in a protest against a decision to unseat 10 Paul delegates from Maine and institute rules changes they believe will weaken their power in the next election cycle.
The changes, approved by the convention on voice votes, will bind delegates to the results of a statewide vote and reduce the role of smaller state-level conventions where Paul had success.
"We were disenfranchised by our party. We won't participate with this chaos," said Russell Montgomery, 52, of St. George, Maine. "We won't legitimize this fiasco. This is as bad as the other party - the corruption."