Tampa, Florida: Forget the loud music, cheering crowds and funny hats. Instead of opening with a bang as originally planned, Mitt Romney’s Republican convention started with a whimper on Monday as party leaders staged a low-key session while Tropical Storm Isaac churned through the Gulf of Mexico.

The tone was deliberately subdued after Isaac led Republicans to scrap most of their first day’s schedule in Tampa, complicating plans to showcase Romney to voters as the presidential candidate heads into a 10-week sprint to his November 6 election battle against Democratic President Barack Obama.

Sunshine broke through the clouds in Tampa as the host city, on Florida’s Gulf Coast, avoided the brunt of Isaac. But a destructive landfall farther north later in the week - possibly at hurricane strength and hitting the Louisiana coast - threatened to create a split screen of TV coverage between the storm and the convention.

With many of the 50,000 delegates still struggling to get to Tampa on storm-delayed flights, organisers mounted a scaled-back agenda on Monday and reshuffled their lineup of speakers into a three-day plan, capped by Romney’s speech on Thursday night.

Romney, who has spent the past few days in New Hampshire practicing for his address, planned to make an early appearance at the convention on Tuesday to hear his wife, Ann, deliver a prime-time address, a campaign official said.

Republicans gathering for the typically festive and partisan event were under pressure to avoid the appearance of unseemly celebration while the Gulf Coast was under threat.

“What would help is if we cut some of the fluff,” said Texas delegate Brad McCally, 32. “I don’t feel like we should have a party. We need to have a little respect for the heartache that Louisiana is going to suffer as the hurricane hits land.”

Isaac swirled across the Gulf of Mexico, disrupting offshore energy production and threatening to hit Louisiana on Tuesday night or Wednesday, the seventh anniversary of Hurricane Katrina.

Reince Priebus, the Republican National Committee chairman, gavelled the convention into session - at least technically - inside a nearly empty sports arena and almost immediately recessed the gathering until Tuesday, when New Jersey Governor Chris Christie will deliver the keynote speech.

Partisan politics were kept to a minimum during the 10-minute session. But Priebus took the opportunity to unveil a “debt clock” that will tally the nation’s red ink during the Republican gathering. The clock, he said, was meant to highlight the “unprecedented fiscal recklessness” of the Obama administration.

Even Obama campaign operatives who came to Tampa to try to counter the Romney team’s message-making were keeping a low profile.

The storm threat also put a damper on early demonstrations, with only about 1,000 protesters - one fifth the number predicted - turning out for a peaceful rally and march on the Tampa Bay Times Forum convention venue.

Republicans seeking to salvage the convention face a stiff challenge: help Romney make an aggressive, memorable argument to be president, while being careful to show sensitivity to those at risk from the storm.

For Romney, the importance of the event cannot be overstated. Running even with Obama or slightly behind him in most opinion polls, Romney needs a bounce in popularity from the gathering, particularly in the 10 or so politically divided “swing states,” including Florida itself, likely to decide the election.

A Reuters/Ipsos online poll released on Monday showed Obama and Vice President Joe Biden leading Romney and running mate Paul Ryan by 46 per cent to 42 per cent. Obama led Romney 54 per cent to 26 per cent in likability.

Romney enters convention week after having made a self-inflicted error by telling a crowd in Michigan that “No one’s ever asked to see my birth certificate,” a joke that rekindled a storyline pushed by far-right conservatives over whether Obama was actually born in the United States.

Romney wants to get the focus on what he considers the paramount issue in the campaign, the weak US economy, telling Fox News he and Ryan would offer “big and bold answers.”

A new Washington Post-ABC News poll showed Romney at 47 per cent among registered voters and Obama at 46 per cent, showing that Romney’s recent selection of Ryan as his running mate did little to alter the close race.

The risk for Romney is that he could be robbed of some media attention - or worse, have images of convention festivities juxtaposed with television shots of the storm’s onslaught - if Isaac dominates the news this week.

Romney remained in New Hampshire rehearsing his acceptance speech.

“We’ve got a great convention ahead,” he said when asked whether he would consider cancelling the gathering in Tampa because of Isaac. “Our thoughts are with the people who are in the storm’s path and hope they’re spared any major destruction.”

In Tampa, part of Republican officials’ aim is to present Romney’s biography - his years as a private equity executive, Massachusetts governor and leader of the 2002 Salt Lake City Winter Olympics - in a flattering way that contrasts with the waves of attacks on Romney by the president and his allies.

The Republicans’ convention was also disrupted in 2008 when they chose to delay its start in St. Paul, Minnesota, as Hurricane Gustav hit the Louisiana coast.

Republicans then were still reeling from criticism of President George W. Bush’s handling of Hurricane Katrina, which devastated New Orleans in 2005. New Orleans is now threatened by Isaac’s projected path.

Top Republicans sought to play down the weather’s impact on the convention as they remained wary of the potential for bad “optics” if Isaac hits the Gulf Coast at the height of their gathering. Organisers have left open the possibility of more scheduling changes or even extending the gathering into Friday.

“Obviously, there is an overlay of concern for the people who are being hit,” US Senator Kay Bailey Hutchison of Texas told Reuters. “But this is the time that has been allocated for the convention, and we are going to just make the best of it like Americans do.”