Mitt Romney vows to restore America's promise
Mitt Romney has pledged "to restore the promise of America", as he accepted the Republican presidential nomination at the party's convention in Florida.
Mr Romney accused President Barack Obama of failing to deliver on his promises and presented his plan involving energy independence, cutting the budget deficit and creating jobs.
He also spoke of his Mormon faith.
The Obama campaign said Mr Romney had "no tangible ideas" and "would take our country backwards".
Mr Romney will challenge the Democratic president in November's election.
His speech was the climax of the three-day Republican convention, which correspondents saw as an attempt to show the human side of a candidate who is sometimes accused of being opaque and distant.
On Friday Mr Romney will visit Louisiana to tour areas damaged by Hurricane Isaac. He will visit LaFitte, some 16 miles (25km) from New Orleans, and a local command centre.
He will miss pre-planned campaign events in Florida and in Virginia to make time for his detour to the storm zone.
Mr Romney began the most important speech of his political career by accepting the nomination that he was overwhelmingly awarded on Tuesday by thousands of delegates at the gala in Tampa.
It secured him the position that eluded him in his first presidential bid in 2008, when Arizona Senator John McCain became the Republican nominee.
"I wish President Obama had succeeded because I want America to succeed," Mr Romney said, in a speech that was watched by millions across the US.
Instead he told his audience: "You know there's something wrong with the kind of job he's done as president when the best feeling you had was the day you voted for him."
And he pledged to do things differently: "President Obama promised to begin to slow the rise of the oceans and heal the planet. My promise... is to help you and your family."
The 65-year-old presidential nominee recounted details of his Mormon upbringing, with anecdotes about his family life and his parents' loving marriage.
Mr Romney talked about his own experiences as a father, apparently becoming emotional as he talked about the times when he and his wife Ann would wake up to find "a pile of kids asleep in our room".
Republican convention video
- Rubio: 'Obama's divide and conquer' 00:25
- Romney: 'I wish Obama succeeded' 04:00
- Ryan sets out vision 01:38
- Romney 'befriended dying teen' 02:22
- Convention-goers fondly recall Bush 02:23
- Clint Eastwood: 'We own this country' 02:43
- Haley Barbour: Romney is 'serious' 01:58
- Three generations discuss US debt 03:12
Mr Romney vowed to create 12 million American jobs over the next four years and turn around an economy saddled with an 8.3% unemployment rate.
He also pledged to make the US energy independent by 2020, cut the national deficit and negotiate new trade agreements.
"I will begin my presidency with a jobs tour. President Obama began his presidency with an apology tour," he said.
He accused the president of having "thrown allies like Israel under the bus", while being too lenient with Iran.
"Under my administration, our friends will see more loyalty and Mr Putin will see a little less flexibility and more backbone," Mr Romney said.
He brought the crowd to its feet when he pledged to repeal Mr Obama's signature healthcare bill.
The event ended with the entire Romney family - his wife, five sons and their wives and most of his 18 grandchildren - on stage with him as thousands of balloons were released over the convention floor.
Republicans at the convention said they were confident of victory after the speech.
"It's been great. It's fired us up. We're going forward. We're going to make it happen," one delegate told the BBC.
"This is just the cherry on the whipped cream, on the ice cream, and we're going to win in November, and there's no stopping it now. This is the wind that's going to blow us into office," said another.
But Mr Obama's campaign manager Jim Messina said the address contained little substance.
"Much like the entire Republican Convention, Mitt Romney's speech tonight offered many personal attacks and gauzy platitudes, but no tangible ideas to move the country forward," he said.
"What he didn't share were his actual proposals, which would take our country backwards."
Attendees in tears
Appearing on stage earlier to pledge his support for Mr Romney, Hollywood star Clint Eastwood raised eyebrows with an off-the-cuff monologue to an imaginary Mr Obama in an empty chair.
Referring to the president, the actor told a rapturous audience: "When somebody does not do the job, you've got to let 'em go."
Democrats have sought to depict Mr Romney as a wealthy, elitist, tax-dodging, corporate raider and policy chameleon. Low favourability ratings have dogged him throughout his campaign and he trails Mr Obama in likeability.
To counter that image, the convention heard emotional testimonials about Mr Romney's work as a Mormon leader that left some attendees in tears.
One couple talked of how Mr Romney had befriended and comforted their dying teenage son.
A woman recalled how the Republican's "eyes filled with tears" when her premature baby daughter was close to death in hospital.
On Wednesday, Mr Romney's running mate, Paul Ryan, pledged a "turnaround" for America, while attacking Mr Obama.
But fact-checkers said there were a number of inaccuracies in the Wisconsin congressman's address.
The job of softening Mr Romney's edges also fell to his wife, who brought down the house on Tuesday with a speech about their high-school romance.