Former Massachusetts Governor Mitt Romney swept to the Republican presidential nomination in US on Tuesday night at a storm-delayed national convention, every mention of his name cheered by delegates eager to propel him into a campaign to oust President Barack Obama in tough economic times.

Romney watched on television with his wife, Ann, at a hotel suite across the street from the hall as the convention sealed his hard-won victories in the primaries and caucuses of last winter.

"I read somewhere that Mitt and I have a 'storybook marriage', she said in excerpts released in advance of a primetime speech meant to cast her multimillionaire-businessman-turned-politician husband in a soft and likable light. "Well, in the storybooks I read, there were never long, long, rainy winter afternoons in a house with five boys screaming at once."

"A storybook marriage? No, not at all. What Mitt Romney and I have is a real marriage," she said.

Aides said her husband of 43 years would be in the hall when she spoke.

A parade of convention speakers mocked Democratic incumbent Obama mercilessly from a made-for-television podium, as if to make up for lost time at an event postponed once and dogged still by Hurricane Isaac.

The Democratic president has "never run a company. He hasn't even run a garage sale or seen the inside of a lemonade stand," declared Reince Priebus, chairman of the Republican Party.

"Mitt Romney will preserve this exceptional American legacy. Barack Obama will destroy it," said Janine Turner, an actress and radio host.

To send Romney and ticketmate Paul Ryan into the fall campaign, delegates approved a conservative platform that calls for tax cuts - not government spending - to stimulate the economy at a time of sluggish growth and 8.3 percent unemployment.

Polls make the race a close one, to be settled in a string of battleground states where neither Romney nor the president holds a secure advantage. More than $500 million has already been spent on television commercials by the two candidates, their parties and allied outside groups, with millions more to come.

Romney's convention victory was more than five years in the making. He was defeated in his first try for the nomination, in 2008, when he was assailed as a false conservative after a term as governor of Massachusetts.

This time, he had the most money, the largest organization and allies with the deepest pockets, all the better to bludgeon Newt Gingrich, Rick Santorum and other rivals in television ads across a string of hard-fought primaries and caucuses. Even so, conservatives were slow to warm to him, and it took longer than many anticipated for him to lock up the nomination.

Even at the convention, a residue of the struggle for the nomination was evident.

Texas Rep. Ron Paul, who never won a primary or caucus, drew several dozen delegate votes - precisely how many were not announced from the podium. Earlier, his supporters chanted and booed after the convention adopted rules they opposed, but were powerless to block, to prevent those votes from being officially registered. "Shame on you," some of his supporters chanted from the floor.

Boehner, presiding over the roll call, made no attempt to have Romney's nomination made by acclamation, even though Ryan's was a few moments later.

The night was Romney's for sure, but some of the loudest cheers were accorded Wisconsin Gov. Scott Walker, a hero among Republicans for fending off a labor-backed recall attempt last spring.

Convention planners squeezed two days of speeches and other convention business into one after scrapping Monday's scheduled opener because of fears that Isaac would make a direct hit on the Florida Gulf Coast.

That threat fizzled, but it was instantly replaced by another - that Republicans would wind up holding a political celebration at the same time the storm turned its fury on New Orleans, devastated almost exactly seven years ago by Hurricane Katrina.