TAMPA, Florida (AP) ― The storm-shortened Republican National Convention begins in earnest Tuesday, a three-day coronation of Mitt Romney as the party’s rival to President Barack Obama. Republicans seek to use the high-profile stage to rally their base, win over undecided voters and humanize a candidate often seen as aloof and wooden.

Once the scene of dramatic floor fights and backroom deals that determined nominees, U.S. political conventions are now carefully orchestrated spectacles with few surprises. Romney locked up the nomination months ago so there will be no mystery in the roll call of state delegates affirming his nomination Tuesday.

Still, conventions are among the most closely watched events in the campaign, allowing the candidates to lay out their visions directly to millions of television viewers and marking the start of the final stretch in the marathon presidential race.

And even the most carefully crafted convention inevitably has surprises ― such as the cancellation of the first day’s activities Monday because of Tropical Storm Isaac.

Republican Party Chairman Reince Priebus gaveled the session to order Monday, then immediately recessed it.

Though the storm no longer threatens Tampa, it could affect the convention. It could reach hurricane strength and make landfall along the northern Gulf of Mexico coast, forcing Romney to share the spotlight.

Republicans may also have to scale down their celebration so they are not seen as partying as the storm barrels toward land. Democrats have sought to cast Romney and fellow Republicans as indifferent to the hardships of non-wealthy Americans and Republicans recall how President George W. Bush was roundly criticized for his handling of Hurricane Katrina in the same region that killed 1,800 people almost exactly 7 years ago. Bush is not attending the convention.

“You can tone down the happy-days-are-here-again a bit,” said Rich Galen, a veteran Republican consultant in Washington. “Maybe you don’t have the biggest balloon drop in history.”

Romney said Tuesday that he hoped those in the storm’s path would be “spared any major destruction” but indicated there were no thoughts of canceling the convention. “We’ve got a great convention ahead,” he declared at his summer home in New Hampshire.

There was speculation that the Romney would make an unannounced visit to the convention hall Tuesday night when his wife, Ann, was on the speaking program. The campaign would confirm only that he was flying to Tampa in time to do so.

The Republican gathering, followed by next week’s Democratic convention, comes as opinion polls show the presidential race nearly even, although it appeared Obama had a slim advantage in battleground states where the election is most likely to be decided.

Obama’s approval ratings, which soared early in his presidency, have tumbled as he deals with stubbornly high unemployment. Romney, the former head of a private equity firm and governor of Massachusetts, has claimed his business and management background gives him the skills to turn the economy around.

But Obama remains more popular personally. He and other Democrats have attacked Romney’s experience heading Bain Capital, claiming it made a fortune for investors while bankrupting some companies and laying off workers.

Republicans will look to use the convention to counter those attacks and shift the debate to Obama’s stewardship of the economy. It is widely seen as their strongest issue, but they have struggled to keep it at the top of the political agenda. Romney had to fight off Republican rivals in a months-long primary battle and has had to defend himself against attacks on his Bain record and questions about his taxes and offshore accounts.

Last week, political headlines focused on remarks about rape and abortion by a Republican senatorial candidate from Missouri, Rep. Todd Akin, who said a woman’s body has a way of preventing pregnancy in cases of “legitimate rape.” Akin apologized for his claim, which is unsupported by medical evidence, but refused to get out of the race despite the request of Romney and other leading Republicans.

Romney’s candidacy has received only lackluster enthusiasm among some Republicans who question his commitment to conservative positions given his more moderate stances on abortion, gay rights and gun control as governor of Massachusetts, a liberal, traditionally Democratic state. Republicans are increasingly energized and influenced by the anti-tax, small-government-oriented tea party movement, whose members tend to see political moderation and compromise as akin to betrayal.

But Romney thrilled conservatives by naming one of their favorites, congressman Paul Ryan, as his vice presidential running mate.

The convention offers Romney a chance to shore up his support among social conservatives in the party’s base. But he may have added to their concerns Monday when he said in a CBS television interview that he opposes abortions except “in the case of rape and incest, and the health and life of the mother.”

That affirmed his difference of opinion on the subject with Ryan as well as his party’s convention platform, which opposes all abortions. There was no immediate reaction from delegates, who were looking forward to the convention as a final push toward the election.

But regardless of their views on Romney, Republicans are united in their eagerness to defeat Obama.

“There’s a mission here,” said Gary Harkins, a delegate from the southern state of Mississippi. “We have to nominate a candidate for president. Our mission is to save America from becoming a socialistic state.”

Ryan, speaking in his hometown of Janesville, Wisconsin, before heading for the convention, said the Obama presidency has been a failure, and Romney offers a different course.

“We’re not just picking the next president for a few years,” he said. “We are picking the pathway for America for a generation.”

Romney’s acceptance speech Thursday night will be the highlight of the convention. Other major events include a speech Tuesday by Romney’s wife, Ann, and the keynote address by New Jersey’s colorful governor, Chris Christie. Ryan delivers his acceptance speech Wednesday.

Democrats, for their part, said that if the Republican convention proceeds as planned Tuesday, they would resume their on-site efforts in Tampa to counter the Republican message. Democrats had several employees who worked for companies adversely impacted by Bain in Tampa to talk to the media.

In Washington, aides said Obama was being updated at the White House on the storm. He was still planning a two-day campaign trip to the battleground states of Iowa, Colorado and Virginia, beginning Tuesday morning. The U.S. president is not chosen according to the nationwide popular vote but in state-by-state contests.

In a boost to Obama’s convention, Florida’s former Republican Gov. Charlie Crist was added as a speaker. Crist had announced on Sunday that he was endorsing Obama, saying he was the correct choice and criticizing his former party for moving too far to the right.

In the streets surrounding the convention hall, police vastly outnumbered protesters. There was one arrest, a man who refused to remove his bandana after a march through downtown.