Sen. John Ensign (Nev.) — once one of the GOP’s rising stars — stepped down from his position as chairman of the Senate Republican Policy Committee on Wednesday as fallout from a sex scandal threatened to permanently knock him out of leadership.

Ensign acknowledged Tuesday evening that he had an affair with a former campaign aide. The staffer is reportedly Cynthia Hampton, who is married to Ensign friend and former administrative assistant Doug Hampton.

The immediate aftermath has sent Ensign into seclusion in Nevada, and he is not expected to return to the Senate before the July Fourth recess, GOP aides said.

But a leadership race to replace Ensign as the No. 4 Republican in the Senate appears to have been averted, for now.

Sen. Orrin Hatch (Utah) said Wednesday afternoon that he was interested in the post, which is being sought by Republican Conference Vice Chairman John Thune (R-S.D.). But Hatch declared himself out of that race a short time later.

In the long term, Republican aides said speculation about further disclosures from Ensign’s private life, including an alleged blackmail scheme, put Senate Republicans on edge and could further erode his position with his colleagues and voters.

Publicly, most lawmakers sought to avoid commenting on the affair or Ensign’s decision to step down from leadership.

“I’m just not going to comment on it. John has admitted what he’s done. He’s worked hard to build his marriage back in the last six months, and he’s doing what he needs to do as a man,— said Sen. Tom Coburn (R-Okla.), who rooms with Ensign in a Christian-oriented group house in Washington, D.C.

Sen. Jim DeMint (R-S.C.) — who shares the same home — declined to comment directly on the affair, although he indicated Ensign’s lawmaker roommates were not aware of the affair before his announcement.

“I don’t want to get into that really. I certainly didn’t know until yesterday what he announced. So I think everybody was surprised,— DeMint said.

When they did speak about the affair, most Republicans tried to put a human face on the scandal, arguing that no one is perfect and that it is a largely personal matter.

“I’m certainly praying for the Ensign family. I understand the personal difficulties. They’re certainly in all of our prayers,— said Sen. David Vitter (R-La.), who got caught up in the “D.C. Madam— prostitution scandal in 2007.

“Lord knows if we kicked everyone out of here for every mistake, we’d be short-handed forever,— Sen. Saxby Chambliss (R-Ga.) said.

But privately, Republicans worried about more repercussions. According to several Republicans, Ensign told colleagues and others close to him that he was the subject of a blackmail scheme because of the affair.

Ensign’s office has declined to comment on whether he was extorted — and if so, whether he paid any funds to his blackmailer. But if he did, it could force the hand of the Ethics Committee to investigate how he made those payments.

Federal financial disclosure laws would not require him to list the payments as a liability in his financial disclosure forms, and he would likely be free to pay it out of his own pocket. However, the use of campaign funds as hush money is illegal. Any use of federal funds — if, for example, the blackmailer was a staffer or otherwise employed by the Senate — would also be illegal.

Additionally, if Ensign’s father, who is a wealthy casino owner and developer in Nevada, arranged to finance any payments, that could be viewed as a gift under Senate rules.

Ensign has long been seen as one of the GOP’s up-and-comers — a charismatic lawmaker who could carry the party’s conservative message to independent voters.

Ensign was at the forefront of calls for former Sen. Larry Craig (R-Idaho) to resign after Craig pleaded guilty following a sex sting in a Minneapolis airport men’s room, and he has been a strong supporter of anti-abortion and anti-gay-marriage legislation.

Although he has repeatedly denied eyeing higher office, Ensign recently made a trip to the presidential battleground state of Iowa and has used his position at the Policy Committee to build a national platform for himself.

Republican aides said that if the scandal is limited to the affair, history indicates he could recover at least some of his position. Several aides pointed out that Vitter’s troubles did not weaken his position with his colleagues, while former Speaker Newt Gingrich (R-Ga.) is widely considered a viable candidate for the party’s presidential nomination in 2012 — despite acknowledged affairs and having sought a divorce while his then-wife was in the hospital with cancer.

Republicans said it is too soon to gauge the political fallout from the scandal.

“I don’t know. I think the future determines that. He is a bright young man, and lots of people make mistakes,— Coburn said.

DeMint said he is unsure what effect the scandal will have on his long-term position within the party.

“I don’t know. I really can’t say. I think John Ensign is a great friend, and I think he is a great leader and obviously my hope is that he’ll continue to serve in the Senate for a long time, so that’s really up to the people of Nevada,— DeMint said.

But DeMint acknowledged the credibility gap for politicians has widened over the past few years and that for members of a party that places as much emphasis on family values and morality as the GOP, the appearance of hypocrisy can be difficult to shake.

“All politicians have a credibility problem right now, and it’s up to us to earn the trust of the American people … and the thing is people don’t like hypocrites. We’ve got to live up to what we say,— he said.

Emily Pierce, Jessica Brady and David M. Drucker contributed to this report.