Delegates at the Republican Convention
Mitt Romney has been officially selected as the Republican presidential nominee at the party's national convention in Tampa, Florida.
Delegates from all US states and territories convened to pledge their votes to the former governor of Massachusetts.
He will challenge Barack Obama in November's presidential election.
Recent opinion polls show Romney and the Democratic president locked in a tight race.
Romney, 65, needed to attract at least 1,144 delegates' votes to secure his party's nomination, and the votes from the New Jersey delegation put him "over the top".
Minutes later, Wisconsin Congressman Paul Ryan was formally selected as the Republican vice-presidential candidate.
Ann Romney's moment
Romney was chosen in a lively voice poll during which state delegates called out their team's allocation of votes.
Altogether, Romney secured 2,061 votes, House of Representatives Speaker John Boehner announced to the floor of the convention.
Romney had amassed enough delegates to secure the nomination in May, after a gruelling season of state-by-state primary elections.
But his selection in Tampa put the party's formal stamp of approval on his campaign.
Convention speakers attacked Obama throughout the session.
Republican National Committee chairman, Reince Priebus said the president has "never run a company. He hasn't even run a garage sale or seen the inside of a lemonade stand."
Meanwhile, Boehner said: "His record is as shallow as his rhetoric."
Ann Romney as well as South Carolina Governor Nikki Haley and New Jersey Governor Chris Christie took to the podium on Tuesday evening.
Mrs Romney's speech shed light on what her husband is like in private since Romney, formerly a business star and governor of Massachusetts, is seen as something of an unknown quantity by many voters.
The would-be first lady spoke about her marriage and the way her husband helped her deal with multiple sclerosis and breast cancer.
Mrs Romney, 63, said: "This is the man America needs. This man will not let us down."
Mrs Romney also dispelled any notion that she has had a "storybook marriage".
"Well, in the storybooks I read, there were never long, long, rainy winter afternoons in a house with five boys screaming at once."
Vice-presidential candidate, Ryan is scheduled to speak on Wednesday evening, while Romney's speech is due on Thursday.
The convention also approved its party platform - a policy agenda that calls for tax cuts to revive the economy, repealing and replacing a healthcare law passed by Obama, and an end to abortion.
Recent opinion polls have indicated that voters view the economy and unemployment, which is stuck at 8.3%, as top priorities.
The platform also calls for the overturning of measures passed to regulate Wall Street in the wake of the 2008 economic collapse.
On abortion, the platform says: "The unborn child has a fundamental individual right to life which cannot be infringed."
That is more conservative than Romney's declared view - he says he opposes abortions, except in cases of rape, incest, or when the mother's health is in danger.
This is Romney's second run for the White House, after an unsuccessful bid in 2008.
President Obama's renomination will be confirmed next week at the Democratic National Convention in Charlotte, North Carolina.
This year's convention got off to a late start when Monday's programme was postponed amid concerns that Hurricane Isaac might disrupt the proceedings in Tampa.