“The safety of those in Isaac’s path is of the utmost importance,” tweeted Mitt Romney, his formal nomination as presidential candidate pushed back by a minimum of 24 hours from Monday night to Tuesday.

The announcement was made as delegates and other convention-goers flocked to the Tampa Bay area by the planeload for what had been scripted as four days of political pageantry and speechmaking with a purpose — to propel Romney into the fall campaign against President Barack Obama.

Officials said they hoped to begin laying out a revised schedule on Sunday.

Romney campaigned in battleground Ohio during the day, pledging to help female entrepreneurs and innovators who are eager to create small businesses and the jobs that go with them. It was an economy-themed countdown to a convention taking shape in a city already bristling with security — and bracing for a possible hurricane.

“Women in this country are more likely to start businesses than men. Women need our help,” said the Republican presidential challenger, eager to relegate recent controversy over abortion to the sidelines and make the nation’s slow economic recovery the dominant issue of his convention week.

Reince Priebus, the Republican Party chairman, told reporters on an early evening conference call that no state delegations had changed their travel plans because of the storm. “Everyone is planning on being here and we hope we are up and running and expect all of our delegates to be here,” he said.

Yet with rain and high winds in the forecast, and with the threat of a storm surge and possible flooding, convention organizers said they were making contingency plans to move delegates who have been booked into beachfront hotels to other locations if necessary.

North Dakota Republican Party Chairman Stan Stein said he needed instructions on preparing emergency kits for the 65 to 70 people in his state’s contingent staying at a hotel 200 yards off the water in Treasure Island. “We do blizzards. We can handle them, but we’re just going to go on the advice we’re getting from hotel management on how to prepare for this,” he said.

“Our first priority is ensuring the safety of delegates, alternates, guests, members of the media attending the Republican National Convention, and citizens of the Tampa Bay area,” convention CEO Bill Harris said in an emailed announcement that followed private conversations involving Romney’s campaign, Florida Gov. Rick Scott’s office, security officials and others.

The announcement said that while the convention would officially be gaveled into session on Monday as scheduled, the day’s events would be cancelled until Tuesday.

The announcement made the GOP convention the party’s second in a row to be disrupted by weather. Four years ago, the delegates gathered in St. Paul, Minn., but Hurricane Gustav, slamming the Gulf Coast, led to a one-day postponement.

In that case, party officials rewrote their script to make President George W. Bush’s speech into a video appearance, and to cancel plans for Vice President Dick Cheney to appear before the delegates. Both men were unpopular at the time.

Four years later, there was no immediate sign that Romney’s forces would do anything other than squeeze two nights’ of platform programming into one. Nor did it appear the postponement would cost them much in political terms, since the television networks had already announced they would not be carrying any of Monday’s events live.

Despite the disruption, Priebus said, “we are optimistic that we will begin an exciting, robust convention that will nominate the Romney-Ryan ticket.”

Plans had called for the convention to open Monday with quick ratification of a conservative platform expected, followed by Romney’s nomination in a traditional roll call of the states timed for network evening news coverage.

Barring further postponements it will end Thursday with his prime-time acceptance speech, which aides hope will propel him into a successful fall campaign and, eventually, the White House.

The polls made the race a close one, narrow advantage to Obama, as two weeks of back-to-back conventions approached. Hundreds of millions of dollars have been spent on television ads, with hundreds of million more to come, almost all of it airing in a small group of battleground states expected to settle the election.

The list included Florida as well as North Carolina, where the Democratic National Convention will be held in one week’s time.

Scott declared a state of emergency earlier in the day as the storm approached the Florida Keys, more than 400 miles from Tampa. Forecasters said it was on a track to head west of the convention city, but predicted strong winds and rain at a minimum on Monday as the delegates were to board buses for their first trip to the hall.

“We are a hospitality state. We know how to take care of people and we want to ensure their safety,” Scott said.

Apart from weather concerns, a heavy security presence was already in evidence. Miles of fencing were designed to create a secure zone around a tract of land that included the convention hall, the hotel where Romney will stay and a nearby convention center where journalists and others worked.

Obama did his best to intrude on the Republican unity tableau.

In an interview with The Associated Press, he accused Romney of holding “extreme positions” on economic and social issues, while pledging a willingness on his own part to agree to “a whole range of compromise” with Republicans if he is re-elected.

He did not elaborate, but his pledge seemed designed to appeal to independents and other voters who say they are tired of seemingly perpetual campaign bickering and Washington gridlock.

Plans for Vice President Joe Biden to campaign in Florida were cancelled, also because of the threat posed by the storm.

But Romney said Obama’s entire campaign rested on his ability to persuade people to ignore his record and listen instead to his rhetoric.

“It is not his words people have to listen to. It’s his action and his record,” he said in his appearance in Powell, Ohio. “And if they look at that, they’ll take him out of the office and put people into the office who’ll actually get America going again.”

Romney’s speech included an appeal to women made on economic grounds rather than on the basis of social issues like abortion, the sort of approach the Republican hopes will eat into Obama’s polling advantage among female voters.

“I want to make sure that we help entrepreneurs and innovators. I want to speak to the women of America who have dreams, who begin businesses in their homes, who begin businesses out in the marketplace, who are working at various enterprises and companies,” he said.

Romney envisioned an economic resurgence fueled by abundant energy, expanded trade and a skilled workforce. If that happens, “America is going to surprise the world. We’re going to stand out as a shining city on a hill in part because of our extraordinary economy,” he said to the cheers of an estimated 5,000 supporters.

Romney’s determination to turn the attention to the economy follows two weeks of controversy over Medicare, courtesy of Obama’s campaign, as well as abortion, the result of a comment by Rep. Todd Akin, the party’s candidate in a Senate race in Missouri.

Romney joined an unsuccessful effort by party leaders to force Akin to quit his race after he said women who are raped rarely become pregnant, a view unsupported by medical evidence.

He also fought back hard in recent days in person and television advertising against Obama’s allegations that he and running mate Ryan would remake Medicare in a way that would undermine the health of future seniors.