CORAL GABLES, Fla. – For months, as President Bush and Sen. John Kerry have traded biting exchanges from afar, armies of advisers have painstakingly brokered the candidates’ first face-to-face encounter. They’ve haggled over the room temperature, size of the dressing rooms and even whether a buzzer should cut them off when time is up.

But when the two men step onto the stage here tonight for their first debate, the behind-the-scenes bickering will give way to a discussion with far higher stakes. The rivals have a rich opportunity to clarify their diverging views on the prosecution of a war, which for the first time in a generation is interwoven with a race for the White House.

With Bush holding an advantage in national polls and the majority of surveys from battleground states, Kerry believes the prime-time debate offers a critical opportunity to convince millions of Americans he is ready to assume the Oval Office in a time of global turmoil. Bush, for his part, hopes to reassure voters his Iraq policy is the right one.

“Sen. Kerry’s challenge is to take a stand that is different from the president and that is clear so he can avoid being tagged as a flipper,” said Jeff Stein, a professor of communication at Wartburg College in Iowa. “The president needs to come off as having a vision for the future, not simply being stubbornly tied to past policies.”

As the candidates made their way to Florida on the eve of the debate, Kerry urged voters in Wisconsin to hold the administration responsible for soaring oil prices that have taken a toll on consumers’ pocketbooks. The president, meanwhile, stopped in central Florida to tour wreckage from the fourth hurricane to strike this state in six weeks.

And from sunrise to sunset, on talk radio and cable television, at rallies and in town meetings, Republican and Democratic strategists fanned out to set the stage for the 90-minute forum at the University of Miami. The debate opens an important, three-week stretch of the race that will give Bush and Kerry more substantive exposure to Americans than at any other point in the campaign.

While the candidates sequestered themselves this week to prepare – Bush at his Texas ranch and Kerry at a resort in the critical battleground state of Wisconsin – both have been testing their lines for months.

In Bush’s signature venue of his re-election campaign, “Ask President Bush forums,” he has tested and adjusted lines before friendly Republican audiences to use against Kerry. And Kerry has been trying out his broadsides against Bush for more than a year during a Democratic primary campaign in which the president was the constant punching bag.

In every campaign since televised presidential debates became ritual with John F. Kennedy and Richard Nixon, these events have offered the potential for a key moment upon which the race can turn. Both campaigns have invested considerable time poring over their rival’s previous debates, hoping to catch any hint of surprise or technique.

Four years ago, Bush showed in his debates with Vice President Al Gore that he had a knack for connecting with average viewers – and voters – as he answered questions by rarely filling his allotted time.

If Bush’s style is staccato, Kerry’s is filled with sustained crescendos. During a debate in the Democratic primary, Kerry became so long-winded that his then rival, now vice presidential candidate John Edwards, declared: “That’s the longest answer I’ve ever heard to a yes or no question.”

With that, the audience roared.

The Bush campaign, with a measure of pre-debate bravado, circulated to reporters Wednesday a slim, black spiral-bound notebook entitled: “Debate Briefing Book for Sen. Kerry.” The 12-page primer brimmed with barbs that Bush has been dishing out to Kerry for weeks on the campaign trail, comparing Kerry’s “current positions” with his “record.”

“You voted for “the wrong war, in the wrong place, at the wrong time,”‘ the mock briefing book advises Kerry. “Now you say the war you voted for made us “less safe.”‘

Karen Hughes, a senior adviser to the president who played a key role in debate preparations, previewed Bush’s plan as she seized on a Kerry interview Wednesday on ABC’s “Good Morning America,” in which he sought to explain his support for the Iraq war resolution and his vote against an $87 billion funding bill for Iraq and Afghanistan.

“We’ve spent the weekend trying to keep up with Sen. Kerry’s rapidly shifting positions,” Hughes said, “which has been a challenge.”

Before Kerry left Wisconsin, where he spent the week preparing for the debate because of its status as a must-win state, he offered a hint of his own plan. In the past two weeks, he has increased the volume on his questions about Bush’s credibility, which aides said he will only intensify during the debate.

“I’m looking forward to tomorrow night,” Kerry told supporters Wednesday, “for an opportunity to be able to share with Americans the truth, not the sound bites, not the advertisements, but the truth.”

Faint praise

Both campaigns went to extreme lengths to portray the opposing candidate as a better debater, offering faint praise as a tactic designed to lower their own expectations.

“I think most Americans know that the president occasionally mangles the English language, mispronounces a few words here and there, and has not spent a lifetime practicing debating, which is what Sen. Kerry has done,” Hughes said. “He’s spent his entire life preparing for this moment, starting in prep school and during 20 years in the Senate.”

Mike McCurry, a senior adviser to the Kerry campaign, responded in kind.

“At the end of the day, President Bush is a likable, affable person. We stipulate that,” McCurry said. “But this is not a personality contest. We are not electing a class president or head cheerleader. We are electing a president of the United States.”

In a conference call, staged specifically to debate the debate, McCurry took matters a step further by lightly insulting his boss. He said jokingly that he wanted to say Kerry had performed so poorly in practice that he lost every single round.

“But,” he told reporters, “they won’t let me tell you that.”