A GOP leader Sunday denied a double standard in pushing Sen. Larry Craig to resign after a sex sting guilty plea, while remaining silent over GOP Sen. David Vitter's involvement with an escort service.

A senior Democrat said a double standard by Republican leaders is exactly what occurred.

Sen. John Ensign, R-Nev., the Senate Republican campaign chairman, said Craig "admitted guilt. That is a big difference between being accused of something and actually admitting guilt."

"David Vitter never did that. Larry Craig did," continued Ensign on ABC's "This Week" program.

Sen. Patrick Leahy, D-Vt. and chairman of the Senate Judiciary Committee, expressed a contrary view on "Fox News Sunday."

"One, I say there's a double standard," said Leahy. "Secondly, I don't think they'll ask him (Vitter) to resign because, of course, he'd be replaced by a Democrat. It's easier to ask Larry Craig to resign because he'd be replaced by a Republican."

Idaho has a Republican governor who will appoint a successor to Craig. Louisiana's governor is a Democrat.

Craig of Idaho pleaded guilty to disorderly conduct in a men's restroom and announced Saturday he will leave the Senate at the end of the month. He was caught in a sex sting at the Minneapolis-St. Paul airport in June and, despite his guilty plea, now insists he did nothing wrong.

Vitter of Louisiana has not been charged with a crime although he acknowledged his Washington telephone number was among those called several years ago by an escort service.

Prosecutors say the escort service was a prostitution ring and have accused the woman who headed it of racketeering.

Craig's conduct was "embarrassing not only to himself and his family but to the United States Senate," said Ensign. Before Craig's announcement, Ensign had strongly suggested that he resign.

Another Republican, Sen. Arlen Specter of Pennsylvania, said on "Fox News Sunday" that Craig should seek to vindicate himself.

"I'd like to see Larry Craig seek to withdraw the guilty plea, and fight the case," said Specter, the top Republican on the Senate Judiciary Committee. "I'd like to see him fight the case because I think he could be vindicated."

Regardless of any legal developments in Craig's case, Republicans clearly would frown on Craig changing his mind about quitting the Senate Sept. 30 — and leaving the party with a festering corruption issue.

Ed Gillespie, President Bush's counselor and a former chairman of the Republican Party, acknowledged that ethical scandals have hurt the GOP. He predicted that by 2008, the party "will not have candidates who have any kind of ethical considerations that will be a concern to the voters."

Gillespie agreed with Ensign that Craig's guilty plea made his case different from that of Vitter.

"The fact is that Sen. Craig pled guilty to a crime, and therefore was convicted of a crime. Sen. Vitter has not been charged with a crime, let alone convicted of one. So there's a pretty big distinction here," Gillespie said on "Fox."

Despite Craig's decision to leave the Senate, Democratic Senate campaign chief Charles Schumer, of New York, sought to keep the corruption issue alive. He accused Republicans of failing to support ethics reform when they were in the majority.

"What the American people are looking for is not a blame game, but who is trying to clean it up," Schumer said on "This Week." "For six years, there was no ethics reform."

The New York senator defended Democratic actions in a new fundraising scandal. A party fundraiser, Norman Hsu, had been a fugitive since failing to appear for a 1992 sentencing.

Hsu, who had pleaded no contest in 1991 to grand theft, turned himself in Friday in California. He raised money for Democratic presidential contenders Barack Obama and Hillary Rodham Clinton.

"We've already given money back," Schumer said. "Nobody knew he was a fugitive. When we found out something is wrong, we returned the money."