Mitt Romney is set to fly to Florida on Tuesday, two days earlier than expected, as he seeks to prevent Tropical Storm Isaac from overshadowing his coronation as the Republican presidential nominee.

In a surprise announcement, aides confirmed only that Romney would be in Tampa, but the expectation is that he will attend the convention as his wife Ann gives the primetime speech on the storm-delayed opening night.

"She's going to do terrific," Romney told reporters in Wolfeboro, New Hampshire as they emerged from a preparation session.

"I like my speech. I really like Ann's speech. Our sons are already in Tampa and they say it's terrific there, a lot of great friends, and we're looking forward to a great convention," the White House hopeful said.

What was scripted as a raucous beginning to four days of choreographed political theater opened with a whimper on Monday as Isaac, poised to become a hurricane over the warm waters of the Gulf of Mexico, hogged the spotlight.

Forecasts put the storm on a direct path to hit New Orleans late on Tuesday, seven years almost to the day after Hurricane Katrina devastated the city and killed 1,800 people in one of the country's worst-ever natural disasters.

In Tampa, Republican National Committee chairman Reince Priebus declared a recess to a largely empty hall less than two minutes after opening proceedings, saying thoughts and prayers must be with the people of the Gulf Coast.

Thousands of jubilant delegates were to formally nominate Romney to take on President Barack Obama in the November 6 election. That roll call will now take place on Tuesday afternoon, possibly with Romney in attendance.

Lying neck-and-neck with Obama in the polls 10 weeks before an election that should have been his for the taking given the sour economic times, Romney hopes to use the event to boost his image and win over undecided voters.

Many Americans do not tune in until the convention season starts -- Obama and the Democrats hold theirs next week in Charlotte, North Carolina -- so Tampa provides Romney with a golden opportunity to reintroduce himself.

"For the Romney folks this is a chance to speak to a lot of voters who have only paid casual attention so far and will tune in to his keynote address on Thursday," Charles Franklin, politics professor at the University of Wisconsin-Madison, told AFP.

"Some will be looking for the first time, others will be reconsidering and open to some change," he said.

The run-up to the convention was marred by incendiary remarks from Todd Akin, a Republican congressman seeking a Senate seat in Missouri, who suggested women's bodies spontaneously prevent pregnancy after a "legitimate rape."

The Romney camp -- which roundly condemned the remarks -- is anxious to get back on message, pressing the case that the former Massachusetts governor and successful businessman understands the economy better than Obama and knows how to get the country back on track.

Ann Romney's speech will try to boost his likability by highlighting his human side, while former Olympians will take to the floor on Thursday to remind Americans that he saved the 2002 Salt Lake City Olympics from bankruptcy.

But the storm could still cast a pall over Romney's big moment, and he must tread a fine line between promoting his political ambitions and showing sensitivity to those in harm's way.

"In purely political terms, there is a lot competing for news attention, the convention versus this hurricane," said Diane Heith, associate professor of politics at Saint John's University in New York.

"The more significant the weather event, the harder it will be for Romney to get out the message the Republican party planned."

Louisiana Governor Bobby Jindal, who was due to speak at the convention, was forced to stay home and prepare for disaster, while vice presidential pick Paul Ryan delayed his arrival in Tampa until Tuesday because of the storm.

Romney aides promised the show would go on largely as planned after they frantically repackaged four days of events into three.

Party officials stress that the main night-time speaking slots on Tuesday and Wednesday -- culminating in Romney's acceptance speech on Thursday after an introduction by rising Hispanic star Marco Rubio -- remain unchanged.

Obama will break with tradition and campaign hard through the event, countering Romney's bid to grab an uninterrupted chance to make his case to voters.

National polls have shown a close race between the rivals for weeks. A Washington Post and ABC News poll out Monday showed Romney one point ahead, 47 percent to 46 percent.

Other surveys show Obama leading in some of the most important swing states that could decide the election.