Former Minnesota governor Tim Pawlenty and former Pennsylvania senator Rick Santorum attend the first Republican presidential debate hosted by Fox News Thursday, May 5, 2011. (Fox News/Fox News)

The opening act in the contest to pick a challenger for President Obama in 2012 proved to be an awkward moment for the Republican Party. Thursday night’s candidate debate did as much to highlight divisions within the party as it did to offer a brief for why the president should be denied a second term.

With many of the party’s potentially strongest candidates either choosing not to participate — or still making up their minds about whether to run — the 90-minute debate offered a platform for second-tier candidates to make their case. They took full advantage of the spotlight, but in the process they offered dissonance in the GOP message along with moments of comedic relief to the audience.

That made for a sometimes-entertaining evening for the audience in the hall and those watching on television. But it probably did little to help Republican voters figure out who has the stature and the strength to take on the president in 2012.

The debate, sponsored by Fox News, came at a moment when Obama’s approval ratings are spiking because of the successful mission that killed Osama bin Laden, though there has been no movement in the public’s view of his handling of the economy. The bin Laden death changed the equation for Thursday’s debate, forcing the candidates onto foreign policy turf, rather than being able to focus on the economy and government spending.

As a result, the five candidates who shared the stage had difficulty making a consistent case against the president. They found his foreign policy lacking, but they also found it necessary to praise the president for the raid in Pakistan that killed the world’s most infamous terrorist.

They reached considerable agreement on economic issues, as they sought to seize on rising gasoline prices, the debt and deficits and the sluggish recovery. But as often they differed on how to deal with Pakistan, on how long to stay in Afghanistan, on what to do about Medicare and Medicaid, and most especially, on social issues. As a result, they couldn’t develop a strong bill of particulars against the president.

Former Minnesota governor Tim Pawlenty hoped to profit from the absence of such potential rivals as former Massachusetts governor Mitt Romney or former House speaker Newt Gingrich. He used his answers to strike out at the president on the economy and particularly on health care, where he said Obama had broken a series of promises about health care, made as a candidate.

But given the rules of fair play and the need to engage everyone in the debate, Pawlenty was often a bystander to candidates with little chance of winning the nomination. That especially included Rep. Ron Paul (R-Tex.), the libertarian Republican who has the same small but passionate following he did four years ago, and businessman Herman Cain, who spoke largely in forceful generalities but got a good response from the audience.

Former New Mexico governor Gary Johnson, an iconoclastic conservative who wants U.S. troops out of Afghanistan immediately, also demanded and got air time that took away from the ability of Pawlenty and former Pennsylvania senator Rick Santorum to take over the debate, as they might have hoped.

As other potential candidates remain on the sidelines, Pawlenty has had the opportunity to raise his profile. Though he remains in single digits in most polls, behind Romney, former Arkansas governor Mike Huckabee, former Alaska governor Sarah Palin, Gingrich and businessman Donald Trump, his stature has risen inside Republican circles.

He was well prepared Thursday night, ready with answers on a range of questions and deft in dealing with the absentees. Given the opportunity to criticize Romney’s Massachusetts health care plan, he mostly demurred, saying it wasn’t fair without Romney being able to defend himself. Asked about Huckabee, he lavishly praised him. “I love the Huck,” he said, perhaps believing the former governor will not run and hopeful for his support.

Not all the absentees got off so easy. Santorum, asked about Indiana Gov. Mitch Daniels’s call for a truce on social issues in order to keep the country focused on the looming fiscal problems, offered a tart response. “Anybody who would suggest we call a truce on moral issues doesn’t understand what America’s all about,” he said.

Pawlenty was betting that being on the stage was better than skipping the debate and offending the voters in South Carolina, which, more than any other state with an early contest, has consistently voted for the GOP’s eventual nominee. In that sense, he may be right.

Romney certainly did not help himself by staying away here, given that he ducked out of the final days of the primary here four years ago. But with the others vying for the spotlight at the same time, Pawlenty had trouble breaking through.

In a few months, what happened in Greenville on Thursday night is likely to be a footnote in the Republican race. By the time of the next scheduled debate in New Hampshire in mid-June, the field could look radically different.

Romney is less likely to skip a New Hampshire debate, given that he must win the primary there next year if he hopes to be the nominee. Gingrich likely will be a candidate, after spending the spring tiptoeing his way toward the starting line.

Other candidates could be in by then too. Daniels will make his decision this month. Trump will decide by early June. So too might Rep. Michele Bachmann (Minn.) and former Utah governor and former U.S. ambassador to China Jon Huntsman Jr. Huckabee and Palin are on longer timetables.

That will give the Republicans a fuller set of choices in the face of complaints that the party is fielding a weak team. But if anything, this opening debate was a reminder that all the Republicans who seek to become Obama’s challenger, those onstage and those who weren’t here, are still at the early stages of developing their candidacies.

Obama has obvious vulnerabilities, particularly on the economy. But the Republicans cannot let their opportunities pass to build the case against him. Thursday was a start, but only a tentative one at best.