BOISE, Idaho – Senator Craig, Republican of Idaho will announce tomorrow he will resign from the Senate amid a furor over his arrest and guilty plea in a police sex sting in an airport men’s room, Republican officials said today.

Dan Whiting, Mr. Craig’s spokesman, said the senator would hold a news conference in Boise tomorrow but would not say whether he will step down. C.L. “Butch” Otter, the governor of Idaho, already appears to have settled on a successor: Lieutenant Governor Risch, according to several Republicans familiar with internal deliberations.

Mr. Craig has been out of public view since Tuesday, but Republican sources in Idaho said he spent Friday making calls to top party officials, including the governor, gauging their support.

There has been virtually none publicly.

Asked Friday at the White House if the senator should resign, President Bush said nothing and walked off stage.

Mr. Craig pleaded guilty to disorderly conduct on Aug. 1, and while he has since said he did nothing wrong, the episode has roiled the Republican Party and produced numerous calls for him to step down.

Republican officeholders and party leaders maintained a steady drumbeat of actions and words aimed at convincing Craig to vacate his Senate seat.

Senator McConnell of Kentucky, the body’s minority leader, called Mr. Craig’s conduct “unforgivable” and acknowledged that many in the rank and file believe Mr. Craig should resign.

An aide said Friday that Mr. McConnell has not talked with Mr. Craig since Wednesday, when GOP leaders asked him to step down from his senior positions on Senate committees. He complied with the request, made just one day after they called for an investigation of Mr. Craig’s actions by the Senate Ethics Committee.

“I am not gay. I never have been gay,” Mr. Craig said at a Boise news conference Tuesday, the last time he has been seen in public. He denied wrongdoing and said his only mistake was pleading guilty to a reduce misdemeanor charge.

Republican officeholders and party leaders want Mr. Craig to give up his seat in the Senate as soon as possible. Their preference, according to several officials, is for a successor to be selected and ready to take the oath of office when the Senate returns from its summer vacation next week.

Republican Party officials said a statement had been drafted at GOP headquarters calling for Mr. Craig to resign. It was not issued, these officials said, in response to concerns that it might complicate quiet efforts under way to persuade Mr. Craig to give up his seat.

Republicans, worried about the scandal’s effect on next year’s election, suffered a further setback today when veteran Senator Warner of Virginia announced he will retire rather than seek a sixth term. Democrats captured Virginia’s other Senate seat from the GOP in the 2006 election and have sought to line up former Mark Warner, the former governor, to run if the seat became open.