The Republican national convention has begun as Tropical Storm Isaac reduced the gala opening of Mitt Romney's party coronation to a symbolic session of less than two minutes.
The US national weather service said late on Monday that Isaac was expected to become a hurricane "soon". At 10:00 local time (03:00 GMT on Tuesday), the storm was about 430km from New Orleans, moving towards the city at a speed of 17km per hour.
The storm was exhibiting sustained winds of 110km per hour, and was expected to make landfall sometime between Tuesday afternoon and night.
The weather service said, however, that it was not expected to be as strong a storm as Hurricane Katrina, which battered the city in 2005.
Wielding a gavel, Republican National Committee chairman Reince Preibus declared a recess at the RNC in Tampa on Monday morning, saying the thoughts and prayers of all must first and foremost be with the people of the Gulf coast.
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The original script had seen Romney formally nominated to take on Barack Obama, the US president, in the November 6 election by thousands of delegates, launching a succession of well-honed speeches by leading party figures.
That roll call will now take place on Tuesday afternoon as the convention in Tampa, Florida gets under way for real.
Lying neck-and-neck with Obama in the polls 10 weeks before election day, Romney hopes to use the convention to recast his image after months of damaging White House attacks on his tax secrecy and business record.
As the storm gathered strength, Obama declared a state of emergency in Louisiana on Monday, seven years after New Orleans was pummelled by Hurricane Katrina.
Obama informed the Gulf Coast state's governor, Bobby Jindal, that he was taking the move to free up federal funds and aid, during a conference call with local officials preparing for the storm, expected to come ashore on Tuesday.
"The president directed Administrator [William] Fugate to ensure that FEMA was prepared regardless of the ultimate strength and impact of the storm," the White House said in a statement.
Many US voters do not tune in until the convention season starts - Obama and the Democrats hold their convention next week in Charlotte, North Carolina, - so Tampa provides Romney with a golden opportunity to reset the narrative.
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 is thus anxious to get the campaign back on message, billing the former Massachusetts governor as a successful businessman with the acumen to turn around the flagging US economy and get the country back on track.
A convention speech on Tuesday by Romney's wife Ann will highlight his human side, while former Olympians take to the floor on Thursday to remind Americans that he saved the 2002 Salt Lake City Olympics from bankruptcy.
But the storm presents the candidate with the spectre of a natural disaster casting a pall over his big moment, and he must tread a fine line between driving his political ambitions and showing sensitivity to those in harm's way.
"Our thoughts are with the people that are in the storm's path and [we] hope that they're spared any major destruction," Romney told reporters at his New Hampshire home, as he prepped for Thursday's primetime acceptance speech.
The fate of the convention lay in Isaac's hands as it barrelled towards Louisiana. It was expected to make landfall as a category one hurricane late Tuesday or early Wednesday, right on the eve of Romney's address.
Louisiana Governor Jindal, another high-profile convention speaker, 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 as they frantically repackaged four days of events into three, shortening speeches, moving others and postponing sideline briefings and events indefinitely.
Party officials stressed 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, remained unchanged.
Events prompted ironic jibes that God must be a Democrat as they echo a similar scenario in 2008, when Republicans cancelled nearly all of the first day of their convention in Saint Paul, Minnesota, due to Hurricane Gustav.
Jeb Bush, then Florida governor, was also forced to stay in his home state in 2004 to deal with the aftermath of Hurricane Charley instead of addressing the New York convention to re-nominate his brother, president George W Bush.
Forecasts put Isaac on a direct path for New Orleans, seven years after Hurricane Katrina devastated the city and killed 1,800 people in the country's worst natural disaster in living memory.
National polls have shown a neck-and-neck race between Romney and Obama for weeks. A Washington Post and ABC News poll out Monday showed the challenger one point ahead, 47 per cent to 46 per cent.
Other surveys show Obama with crucial leads in some of the most important swing states that could decide the election.