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TAMPA (CNN) — Mitt Romney arrived Tuesday at the shortened Republican National Convention in Tampa as organizers kept a nervous eye on Hurricane Isaac churning toward Louisiana’s coast.

The storm caused a one-day delay in the convention agenda, but Republican officials appeared determined to stick to the condensed three-day schedule that kicks off with official business Tuesday afternoon, followed by a series of speeches in the evening.

Among the planned events later Tuesday are the roll calls of the delegates that will show that Romney has locked up the necessary support for the party’s nomination. However, organizers who previously described the roll call as the nominating process said Tuesday that the formal nominations of Romney and running mate Rep. Paul Ryan of Wisconsin won’t occur until Thursday, the last day of the convention.

“We are running through the roll call tonight,” Romney campaign strategist Russ Schriefer said. “Gov. Romney will not be nominated, however, until Thursday. We will complete the roll call — Gov. Romney will get the 1,144 delegates that are necessary — but the actual nomination will occur on Thursday.”

Still, Romney and his wife, Ann, flew into Tampa on Tuesday morning and arrived at the downtown convention site two hours before the proceedings were scheduled to begin. Ann Romney is one of the featured speakers Tuesday night.

Organizers acknowledged they were monitoring the storm projected to make landfall in Louisiana as early as Tuesday evening, just a day before the seventh anniversary of devastating Hurricane Katrina hitting the state.

Their concern is the perception of a celebratory convention atmosphere with colorful balloons and soaring rhetoric as a hurricane slams into the Gulf Coast, evoking memories of the havoc caused by Katrina and the ensuing criticism of the Republican administration’s response.

However, Romney and Republicans are reluctant to lose any more of their best opportunity to define the candidate for the American people with less than three months until the election.

The 2,200-plus delegates on Tuesday will vote on a conservative party platform and hear speeches from Ann Romney and top Republican politicians, including the keynote address by New Jersey Gov. Chris Christie.

“I packed a flashlight! Never done that before,” Cyndy Aafedt of North Dakota told CNN. “I even went and bought batteries before I came.”

So far, the biggest casualty of the shortened schedule has been a planned appearance by Donald Trump. The real estate mogul and outspoken conservative was going to take part Monday.

Republicans say the convention must focus on Romney’s character and show how he can lead the nation to economic prosperity, which is the top issue with voters.

“It’s the vision of Mitt Romney versus the record of Barack Obama, and facts just are stubborn things,” Virginia Gov. Robert McDonnell told ABC on Sunday, adding that “the middle class is hurting” and people want “results, not rhetoric.”

The Obama campaign, anticipating the Romney branding effort by Republicans, released a movie trailer-style video Sunday that previewed a “do-over” moment for Romney.

In a statement accompanying the video, the Obama campaign said it is “presenting Americans with an epic cinematic preview of Mitt Romney’s ‘convention reinvention’ — the Do-Over moment that voters have grown to expect — because they’ve seen this movie before.”

Responding to the video, Romney’s campaign said Sunday the president was relying on “negative attacks” as a way to distract from his own record.

Last week, controversial comments by conservative Republican Rep. Todd Akin of Missouri ignited a political firestorm about rape and abortion as the Romney team sought to build momentum up to the convention.

Akin, who won Missouri’s Republican Senate primary to challenge Democratic Sen. Claire McCaskill in November, told an interviewer that women have an undefined biological response to what he called “legitimate rape” that oftentimes prevents pregnancy.

Romney and a full spectrum of GOP politicians, from the RNC to tea party groups, condemned Akin’s comments and called for him to drop out of a race considered crucial to Republican hopes of winning a Senate majority.

Akin apologized and called his remarks incorrect, but he has refused to end his U.S. Senate bid. The imbroglio has given new life to McCaskill, considered the most vulnerable Democratic senator running, and caused chagrin within the Republican establishment.

Republican strategist Karl Rove kept up the criticism of Akin on Monday, telling a breakfast in Tampa hosted by Politico that Akin “said a really stupid, indefensible thing from which there is no recovery, and if he really cares about the values of conservatism and pro-life, he will not go down for defeat as the biggest loss by a Republican candidate for Senate in modern history.”

Some conservatives, including former Arkansas Gov. Mike Huckabee, have defended Akin’s decision to stay in the Missouri race, but Rove was unmoved.

“I talk to some conservatives who say, ‘It’s not fair. We have to stand with him,’ ” he said. “Well, it is unfair. I get that. But it was also incredibly wrong, and there was no recovery from it. It would be one thing if it was some minor misstatement. But this was pseudo-science and morally incomprehensible.”

A further concern is that Akin’s comments focused attention on the volatile abortion issue in the run-up to the convention, when the Romney campaign wanted to talk about the candidate’s prescriptions for high unemployment and slow economic growth under Obama.

Instead, Romney and Ryan, the conservative House Budget Committee chairman, have been asked repeatedly about differences between their personal views on whether abortion should be banned in all cases or permitted only for pregnancies from rape, incest or that threaten the life of the mother.

Romney’s Mormon faith supports the narrow exceptions, while Ryan, a devout Catholic, supports a blanket ban. The campaign has made clear the ticket supports Romney’s stance, which also contrasts with the party platform.

CNN’s Kevin Bohn, Paul Steinhauser, Dana Davidsen, Ashley Killough, Dana Bash, Deirdre Walsh, Halimah Abdullah, Martina Stewart and Mark Preston contributed to this report.