Peter Wallsten, Los Angeles Times

A PBS video previewing its Republican presidential candidates' forum, set to air tonight from a historically black university, asks: "Can the party of Abraham Lincoln win the hearts and minds of all Americans?"

But none of the GOP's top White House contenders will show up to answer the question, each citing a scheduling conflict. Instead, viewers will see four empty podiums on the stage as Tavis Smiley, a black talk-show host, poses questions to five lesser-known candidates.

Coming days after the Spanish language network Univision was forced to postpone its Republican forum because it was rejected by all but one candidate -- Sen. John McCain of Arizona -- the PBS forum has touched off a debate within the GOP over whether its 2008 candidates are trampling on past efforts to draw more minority voters.

"It's a missed opportunity," said former Maryland Lt. Gov. Michael Steele, who would have been the Senate's only black Republican had he won his election bid last year.

Steele, an organizer of the PBS forum, said he had confronted the campaigns in recent days to no avail, warning them that failing to connect with black voters would be "lethal" in next year's general election.

Other Republicans have weighed in as well, including former House Speaker Newt Gingrich and J.C. Watts, a former congressman from Oklahoma. Watts, who is black, told ABC's "Good Morning America" this week that the candidates were "stupid" to skip the forum.

"You kind of scratch your head thinking, 'Why are they making decisions like that?' " Watts said.

Smiley said he does not believe the campaigns when they blame their absences on hectic schedules.

"When you consistently [turn down] invitations to appear in front of black and brown audiences, I tend to think that's a pattern and not a scheduling problem," Smiley said Wednesday.

Just last year, the GOP backed three black candidates in major statewide races, and party leaders were promising aggressive outreach to black voters as part of a broader strategy to build a long-lasting majority. Many believe that President Bush's courtship of blacks in certain states ensured his re-election victory in 2004.

Critics say the 2008 candidates' decisions reflect the reality that the Republican nomination will be decided by the party's overwhelmingly white, conservative base. Answering questions on such issues as urban blight, AIDS, the government response to Hurricane Katrina and immigration might only hurt the top candidates, all of whom have faced scrutiny over their conservative credentials.

The candidates' forum absence comes a little more than two years after then-Republican National Committee Chairman Ken Mehlman declared at an NAACP meeting that "we were wrong" when the GOP "gave up on winning the African-American vote, looking the other way or trying to benefit politically from racial polarization."