The first presidential debate, to be held in Denver on Wednesday, could help sway a group of voters who are only halfheartedly committed to either President Obama or Republican presidential nominee Mitt Romney.

Labeled "soft voters" by pollsters, this not-quite-decided group accounts for a relatively thin slice of the electorate. But add them to the 3 percent or 4 percent of voters who have truly not made up their minds about the race, and it's a large enough bloc to sway the election.

"Certainly their target is going to be not only their base, but the soft voter, to see if you can move those soft voters to be more intense," Republican pollster Ed Goeas told The Washington Examiner. "Getting an edge on who has more intensity among their voters is one of the key things the candidates are looking at here."

The two presidential contenders enter their first debate with Obama leading Romney by about 4 percentage points nationally, according to a RealClearPolitics averaging of polls.

Even before Obama and Romney step to the debate podiums for the first time, the vast majority of voters have already decided which of them they'll support. But some voters are less excited about their choice, and those people, Goeas said, can be convinced to change their minds if one of the candidates either wows them in the debates or botches it badly.

"I think, quite frankly, all three of the debates are going to be important," Goeas said. "If you look at how wildly the different candidates went up or down in the polls during the Republican primary, that was driven much more by the debates than the campaigns."

If the candidates avoid any game-changing moments during their meeting and instead turn in two adequate but uneventful performances, that could benefit Romney, Goeas said.

"For the challenger to stand there and appear to hold his own and look presidential and be equal with the president onstage, normally the tie goes to the challenger," he said. "That is what I think the Obama campaign is somewhat worried about."

Ron Faucheux, a pollster and author of "The Debate Book," said that while most debates lack "gotcha" moments, they made a critical difference in the presidential contests of 1960, 1976, 1980 and 2000.

In 1980, the Gallup poll showed then-President Carter leading Republican Ronald Reagan by 8 points just two days before their debate. But then Carter claimed during the debate that he consulted his 12-year-old daughter about nuclear weapons, becoming the butt of late-night comedians' jokes and dropping precipitously in the polls.

A week later, Reagan beat Carter 51 percent to 41 percent.

"Reagan's debate performance in 1980 turned a close race into an electoral blowout," Faucheux said.

Wednesday's debate at the University of Denver will be moderated by former "PBS NewsHour" anchor Jim Lehrer.

It's the first of three presidential debates. The second debate is set for Oct. 16 at Hofstra University in New York and will be moderated by CNN's Candy Crowley. The final debate will be Oct. 22 at Lynn University in Boca Raton, Fla., with Bob Schieffer of CBS questioning the candidates.