Besieged by negative headlines and editorials, embattled Illinois Senate candidate Jack Ryan (R) cancelled a trip to Washington, D.C., today as he begins to reassess whether he can continue his campaign in the wake of damaging allegations from a previously sealed custody file that was made public this week.

Ryan had planned to appear at a morning event showcasing the support of retiring Sen. Peter Fitzgerald (R-Ill.), the man he hopes to succeed, and to attend a noon luncheon with National Republican Senatorial Committee Chairman George Allen (Va.), who has stood firmly behind the nominee despite calls from some Republicans for him to exit the race.

But the trip was scrapped at the last minute, sources said, with Ryan choosing to stay in Chicago to huddle with his advisers.

“The tone seemed to have changed within the campaign,” said one GOP source in Washington. “Now it seems that they’re kind of reassessing the coverage that they’re getting and where they stand on a day-to-day basis.”

Earlier in the week, Ryan canceled a breakfast fundraiser that had been scheduled for this morning, after Speaker Dennis Hastert (R-Ill.) pulled out of his appearance because the event conflicted with a meeting at the White House.

A Ryan spokeswoman told The Associated Press on Thursday that the trip was not cancelled because Ryan is rethinking his candidacy, and she maintained that the nominee is staying put.

While Senate Republicans have stood by Ryan, Hastert has not yet spoken out about allegations made public on Monday that Ryan forced his ex-wife, actress Jeri Ryan, to go to “explicit sex clubs” on several occasions while they were married.

Jeri Ryan, known for her roles on “Star Trek: Voyager” and “Boston Public,” continued to stand by the allegations she made during the couple’s child custody battle in 2000 and 2001.

”Jeri’s statement can be found in the original court documents, and the truth has not changed in the last five years,” a spokesman for the actress told “Entertainment Tonight” on Wednesday. The spokesman also reiterated that Jeri Ryan wishes her ex-husband “the best of luck in his Senate campaign.”

If Ryan withdraws from the race, the state Republican Party’s Central Committee is responsible for filling the vacancy on the November ballot. In March, Democrats nominated state Sen. Barack Obama, who has held wide leads over Ryan in early polling and is viewed as a rising star in the national party. He will give the Democratic weekly radio address this weekend.

If Ryan drops out, several well-known Republicans’ names are being floated to succeed him. They include former Govs. Jim Edgar and Jim Thompson and state GOP Chairwoman Judy Baar Topinka. Topinka is currently the state treasurer and the only statewide-elected Republican aside from Fitzgerald.

While all three of those candidates would be in a position to get a campaign up and running, none is thought likely to volunteer for the race.

More than likely, sources say, Republicans will turn to a wealthy candidate who will be able to self-fund much of the campaign — as one Illinois GOP operative put it, “someone who can write a check on day one.”

Among the candidates being mentioned who fit that bill are paper-company executive Andy McKenna, who placed second to Ryan in the March GOP primary, and Ronald Gidwitz, a member and former chairman of the State Board of Education and former CEO of Helene Curtis Industries Inc., which is now owned by the British-Dutch conglomerate Unilever.