By Lisa Mascaro

Wednesday, Oct. 7, 2009 | 2 a.m.

Behind the closed doors of the Republicans’ exclusive weekly luncheon Tuesday, Sen. John Ensign inserted himself into the policy debate with force, without any of the expected inhibitions of a lawmaker fighting for his political life.

Ensign spoke up on health care reform, mixing it up with colleagues as if it were another day at the office — rather than the first full day back at work after becoming the subject of a Senate Ethics Committee investigation and possible Justice Department inquiry.

Ensign’s stunning and ongoing display of self-confidence appears to be equal parts hubris and survival strategy — as if acting like nothing is amiss makes it so.

Whether Washington can look past the cloud of suspicion hanging over Ensign remains to be seen.

“We are very disappointed,” fellow Republican Sen. Jim DeMint of South Carolina, a housemate of Ensign’s at the C Street Christian home they share with other lawmakers on Capitol Hill, said about the developments. “Obviously, it’s not good.”

The New York Times last week raised new ethical questions about Ensign’s affair with a woman who was on his staff and his actions in its aftermath. At issue is the work Ensign helped to secure for the woman’s husband, Doug Hampton, who also worked for the senator, in possible violation of the one-year ban on Senate staff members lobbying their former bosses.

Legal experts say the new allegations are likely to trigger an investigation. Ethics violations can be criminal offenses and the penalties include jail time.

The return of the Ensign affair is unwelcome for Republicans in Washington and Nevada who hoped the issue had run its course.

The party does not need a drawn-out ethics scandal as it tries to hammer on Democrats’ ethics transgressions. Nor do party leaders want to spend their time answering questions about Ensign’s affair when they could be pressing their case on health care reform, the war in Afghanistan or other issues.

Ensign had all but turned the page on the scandal before last week’s story broke, playing an aggressive role fighting health care reform in the past few weeks as a member of the Senate Finance Committee.

In fact, Ensign was seated in a committee hearing when the Times story sent BlackBerrys buzzing last Thursday. He abruptly left the committee debate, only to return later in the evening and reinsert himself into the discussion as if nothing had happened.

Ensign appeared upbeat Tuesday, saying he felt good but declining most questions.

“I’m fully planning on working, staying in office,” Ensign told the Sun and a few other reporters as he ducked into the luncheon.

Ensign’s office has said he would comply with any official inquiry and has followed all laws.

He received a mixed reaction throughout the day. He was ignored on the Senate floor as colleagues brushed past without so much as a nod, but was chatting in the cloistered Senate cloakroom with other Republicans as the votes dragged into the evening.

Ensign appeared intent on behaving as if nothing had happened, but his ability to carry on with business as usual — let alone lobby his colleagues to join his side in policy matters — remains in question.

He and Senate Majority Leader Harry Reid, his fellow Nevadan, sent out a joint news release Tuesday morning on the future of the Nevada Test Site. But it remains to be seen whether senators who don’t have state issues in common would attach their names to a senator involved in a scandal.

The silence from Republican leaders and colleagues has spoken volumes, as they have again failed to come to his side, much the way they distanced themselves from Ensign when he first disclosed the affair this summer.

Senate Minority Leader Mitch McConnell of Kentucky sidestepped questions last week, declining to comment about the fresh allegations of potential wrongdoing.

When asked whether Ensign should remain in office, Republican Sen. John Cornyn of Texas deferred Tuesday to the Senate Ethics Committee to “make a recommendation.”

The newest member of the Republican leadership team, Sen. John Thune of South Dakota, who took Ensign’s No. 4 position after the Nevadan resigned the leadership post this summer after disclosing the affair, ducked into the lunch, avoiding the question with a short “I’m late.”

Republican Sen. Tom Coburn of Oklahoma said he looks “forward to a good ethics inquiry.” This after having said that he would not testify about the private conversations he had with Ensign and Hampton. Coburn had counseled both men, and the Times said he relayed Hampton’s request for $2 million payment to the senator.

Coburn declined to comment on Ensign’s political future.

Senate rules allow for expulsion with a felony conviction, as was the case when former Republican Sen. Ted Stevens of Alaska was asked to resign after being convicted in a corruption case last year. He lost reelection several weeks later and the guilty verdict was eventually thrown out.

As the Ensign investigation unfolds in the Senate Ethics Committee, sources with knowledge of Senate operations say, there is little leadership could do, other than make the workday uncomfortable, to pressure a colleague to quit.

Leaders have been unable to force out other senators, including Idaho Republican Sen. Larry Craig, who was snared in a men’s restroom sex scandal. Ensign at the time called for Craig’s resignation, but Craig ignored the pleas and simply declined to seek reelection. On the Democratic side of the aisle, Sen. Roland Burris of Illinois continues to serve despite questions surrounding his appointment by former Gov. Rod Blagojevich.

Having the chutzpah to remain in office while under investigation is one thing. Seeking reelection is another.

When Ensign first disclosed his affair this summer, he vowed to stay in office and seek a third term in 2012.

When asked about his reelection plans Tuesday as he ducked into the lunch, Ensign let the door close behind him in silence.