Sept. 28 (Bloomberg) -- The four top Republican presidential candidates came under fire from their rivals for skipping a debate last night that focused on minority issues.

The absence of former New York Mayor Rudy Giuliani, former Massachusetts Governor Mitt Romney, Senator John McCain of Arizona and former Senator Fred Thompson of Tennessee gave the second-tier candidates a rare opportunity to command the spotlight, and they wasted little time criticizing the no-shows.

``I'm embarrassed for our party and I'm embarrassed for those who did not come because there's long been a divide in this country, and it doesn't get better when we don't show up,'' said former Arkansas Governor Mike Huckabee.

Senator Sam Brownback of Kansas said it was a ``disgrace'' that the frontrunners failed to show up. ``I think it's bad for our country and it's bad for our party, and I don't think it's good for our future.''

The debate, carried on PBS, took place at Morgan State University, a historically black school in Baltimore.

All four who missed the debate cited scheduling conflicts. Darrel Ng, a spokesman for Thompson, said that Thompson had a previously scheduled roundtable interview with journalists in Franklin, Tennessee. Thompson has been invited to ``dozens'' of debates and has agreed to participate in many of them, Ng said.

Fund Raising in California

Giuliani ``would love'' to have participated, but was in California yesterday raising campaign funds, spokeswoman Maria Comella said.

Others who participated last night were Representative Duncan Hunter of California, Representative Tom Tancredo of Colorado, Representative Ron Paul of Texas, and Alan Keyes, a conservative commentator and onetime diplomat. All the second- tier candidates are in single digits in the national polls.

Some prominent Republicans, including former Representative J.C. Watts of Oklahoma, have said that the decision by the top candidates to skip last night's debate may harm the party's efforts to court minority voters. Earlier this year, Univision, a Spanish-language television network, scrubbed a Republican debate after only McCain agreed to participate.

To contact the reporter on this story: Edwin Chen in Washington at echen32@bloomberg.net.

Last Updated: September 28, 2007 12:11 EDT