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Illinois Republican leaders asked two-time presidential hopeful Alan Keyes (search) on Wednesday to be their Senate candidate, but like a string of previous possibilities, Keyes said he needed a few days to think about it.

Keyes told a news conference Wednesday night that he would make an announcement by Sunday.

"If I do step forward to pick up that challenge, I will be laying a lot on the line in terms of what I have tried to do in this country," he said.

It's been a laborious six-week search as Republicans have sought a candidate willing to tackle the daunting task of taking on Democratic rising star Barack Obama (search) in the Senate race.

Republican primary winner Jack Ryan (search) dropped his bid amid embarrassing sex club allegations that surfaced when records from his divorce were unsealed in June.

With Keyes and Obama as the candidates, the already closely watched race to fill the seat of retiring Sen. Peter Fitzgerald (search) would draw more national attention: It would be the first U.S. Senate election with two black candidates representing the major parties, almost assuring Illinois would produce only the fifth black U.S. senator in history.

"I think it's a hopeful sign for the country," Obama said Wednesday. "I think obviously when we have 100 U.S. senators and none are African-American, that's something that doesn't just trouble African-Americans, I think it troubles all Americans."

But Keyes' response that he needed time to consider the offer, and likely talk to national Republican leaders about financial help, was an uneasy echo of the party's experience with previous potential candidates. Party leaders have tried to enlist several big-name candidates — former governors, state senators, even Chicago Bears great Mike Ditka (search) — but each ultimately declined.

Obama, a state senator, has a huge head start: He has raised more than $10 million, has drawn thousands of people to campaign stops and gave the keynote speech at the Democratic National Convention last week.

Keyes, a two-time presidential hopeful, hadn't even surfaced as a possible contender until early this week. He missed the scheduled candidate interviews Tuesday, but when the committee narrowed its choices to two that night, Keyes was still in.

As he arrived from Maryland for his first face-to-face interview with the committee Wednesday, Keyes didn't directly say he wanted to run — he said he was there to consult with the party's leadership about the best way to make sure there was an exchange of ideas.

Asked how he felt about making a Senate run from a state he had never lived in, he responded: "As a matter of principle, I don't think it's a good idea.

"It has to be something where I would be convinced it's not only consonant with federalism as I understand it but that it's in the best interest of the state and of the nation," Keyes said.

The other finalist interviewed Wednesday was Andrea Grubb Barthwell (search), a Chicago-area physician and former deputy drug czar in the Bush administration who has little campaign experience and allegations in her past that she had made "lewd and abusive" comments about a colleague's sexual orientation while in Washington.

Barthwell, who has contributed to Democratic candidates, and Keyes are on nearly opposite ends of the Republican Party spectrum.

Keyes, 53, opposes abortion and gay rights, wants to replace the income tax with a national sales tax, thinks parents should be able to send their children to schools that reflect their faith and calls affirmative action a "government patronage program."

Keyes has a Ph.D. from Harvard in government affairs, was appointed ambassador to the United Nations Economic and Social Council by President Reagan and served as assistant secretary of state for international organization affairs before deciding to run for office.

When he first ran for the U.S. Senate from his home state of Maryland in 1988, he also stepped in as the Republican candidate after the primary winner withdrew. Keyes ended up getting only 38.2 percent of the vote.

He did even worse in 1992, when he tried to unseat Sen. Barbara Mikulski, D-Md., amid grumbling by some voters that he had been paying himself a salary out of campaign funds.

But Keyes also is a polished speaker who hosted a syndicated radio show in the 1990s and has frequently appeared as a political commentator.

For the Illinois GOP, having a candidate with high name recognition is vital.

"When Barack Obama got put on a national stage ... suddenly this race took on a greater significance than just the state of Illinois," said Kirk Dillard, a members of the Republican State Central Committee that picked Keyes.

The party has less than three months to get its new candidate's name and believes before voters ahead of the Nov. 2 election. Keyes' out-of-state status is more likely to be a campaign issue than a legal issue: State law requires only that he be an Illinois resident by Election Day.

Although both Keyes and Barthwell are black, members of the Republican State Central Committee that chose the candidate said race wasn't the important factor. The committee wanted "somebody who appeals to a broad spectrum of voters," co-chairman Stephen McGlynn said.