Nevada Republican John Ensign insists he will not resign from the Senate, despite ongoing criminal and ethical investigations into his conduct. Both in Washington, D.C., and Nevada, however, there is growing consensus that he is finished politically. Ultimately his fate will come down to the definition of “finished”—he might be finished in the U.S. Senate, though not back home in Nevada, or vice versa.

For now, the Ensign implosion seems a foregone conclusion, and political operatives have turned their attention to the Gibbons appointment to Ensign’s seat.

But as his tawdry sex, hush money, and influence-peddling scandal has escalated onto the front page of The New York Times, and amid isolation by leaders of his party and calls for his resignation by conservative talk-show hosts, he has thrown the 2010 and 2012 Nevada Senate, congressional, and gubernatorial races into utter chaos.

Ensign now faces expulsion by the Senate for his attempts to obtain lucrative consulting contracts for Doug Hampton, the husband of his mistress, as well as possible criminal charges stemming from rewarding the companies that agreed to hire Hampton by intervening on their behalf with federal oversight agencies. As The Daily Beast reported this summer, on June 16 the Pentecostal senator admitted to his affair with 46-year-old Cynthia Hampton—his campaign treasurer and the wife of his best friend and top aide. At the time of his confession, Ensign was chairman of the Senate Republican Policy Committee and considered a promising presidential contender for 2012.

Although his polls plummeted in Nevada, Ensign seemed to be weathering the storm, until the 4,000-word Oct. 2 story in the Times revived the saga. With painstaking detail, the article described the lengths to which Ensign went to arrange for Doug Hampton to join a political consulting firm, solicit clients for Hampton from government-regulated industries, and then assist those clients with their government relations. Since the publication of the exposé, Ensign has “ taken a beating,” writes Las Vegas journalist and blogger Steve Sebelius.

While it is a long way from newspaper allegations to Senate censure or criminal charges, the conventional wisdom in Nevada is that it is a matter of when, not if, Ensign is forced to resign.

“This is a man accused of an incredible act of arrogance and hypocrisy,” said Michael Green, professor of history at the College of Southern Nevada. “They’re not the same thing. He proceeds to wade into the health-care debate taking the same right-wing, un-Christian positions. Never mind our fellow man. I’ve got to make the president look bad. Did he learn nothing? Compare him to Teddy Kennedy, who committed a heinous act and spent the next 40 years trying to atone for it.”

Las Vegas Sun columnist John Ralston, who has done seminal reporting on the Ensign-Hampton scandal, wrote this week: “If it weren’t true, it would be hard to believe anyone who isn’t a villainous caricature in a novel could act this way. I care less that any laws were broken than that anyone could behave so grotesquely and believe he still warrants the public trust. What kind of man could think that? One not fit to be a United States senator.”

Perhaps the most revealing clue that Ensign is “finished” is a recent Op-Ed by Sherm Frederick—publisher of the ultra-conservative Las Vegas Review Journal, which has continually and consistently defended Ensign. “ I will not use double standards to excuse anyone’s failure to do the public good. If Ensign did so, he should suffer the consequences [whatever it is],” writes Frederick. Also telling is Frederick’s quote on his Facebook page: “John Ensign slips deeper into the darkness of politics as usual.”

Ensign’s Republican colleagues are backing away from him, with Senate Minority Leader Mitch McConnell (R-KY) telling an interviewer, “I really don’t have any observations to make about the Ensign matter.” Even Sen. Tom Coburn (R-OK), one of Ensign’s Capitol Hill roommates who acted as an intermediary in relaying restitution demands of more than $8 million from Hampton to Ensign, distanced himself in an interview with the Times. “John got trapped doing something really stupid and then made a lot of other mistakes afterward,” he said. “Judgment gets impaired by arrogance, and that’s what’s going on here.”

Ironically, Ensign still has a friend in the U.S. Senate, his onetime rival and fellow Nevadan Senate Majority Leader Harry Reid. The two men have abided by a “ nonaggression pact” since 2000, when they agreed to refrain from criticizing each other. A Reid spokesman told the Las Vegas Sun that the Democrat considered the Ensign affair a “personal matter.” Nevada Democrats are ambivalent about Reid’s stance. Some are afraid Reid will alienate his liberal base, which will be offended at his allegiance to the ethically challenged Ensign. Others see it as a classic Reid calculation: A weakened Ensign is to the Democrats’—and Reid’s—advantage.

“They’ve given themselves enough rope. John Ensign is the best thing to happen to us in a long time,” the Las Vegas Sun quoted a Democratic source as saying. “We’re taking the high road and letting Republicans do the heavy lifting for us by calling for him to resign.”

Ensign’s survival depends upon myriad factors, each of which influences a host of equally intriguing scenarios back home in Nevada. Clearly, “ Senator Sanctimony,” as the renowned Las Vegas columnist John L. Smith has dubbed Ensign, intends to hold onto his seat in the U.S. Senate as long as he possibly can. The question, then, is: At what point will the national Republican leadership decide to cut him loose? Probably while Nevada’s Republican governor, Jim Gibbons, is still able to appoint a successor to finish Ensign’s term. The beleaguered incumbent governor has his own set of scandalous problems and is fending off allegations that he assaulted a woman in a Las Vegas parking garage. Although his money has dried up and his poll numbers are in a tailspin, Gibbons insists he is running for reelection next year. He faces a bloody primary against dark-horse candidate Brian Sandoval—the rising star in the Nevada GOP who stunningly gave up his $174,000-a-year lifetime appointment as a federal judge to run against Gibbons. If by some miracle Gibbons beats Sandoval, he will face the rising star of the Democrats, Rory Reid, son of Harry Reid. (Meanwhile, Reid Sr. has a tough reelection race ahead of him, as he squares off against a former head of the state GOP, Sue Lowden, at a moment when he is vulnerable in a midterm election cycle.)

For now, the Ensign implosion seems a foregone conclusion, and political operatives have turned their attention to the Gibbons appointment to Ensign’s seat. An obvious candidate might have been Republican Lt. Gov. Brian Krolicki, if not for the fact that he is under indictment on charges stemming from the mismanagement of a multibillion-dollar college savings plan. Other aspirants include Republican Rep. Dean Heller, who has bowed out of any 2010 races with his eye apparently on challenging Ensign in 2012, and Lowden, who faces an uphill battle against Sen. Reid in 2010.

A politically savvy move on Gibbons’ part would be to appoint Sandoval, his strong, internecine challenger in the governor’s race. But Sandoval, in giving up his cushy lifetime judgeship to run against the über-flawed Gibbons, has shown himself a political and intellectual maverick. Accepting an appointment from Gibbons would be anathema to a man of Sandoval’s stature. The odds in Las Vegas should be on Gibbons appointing Gibbons. Legal technicality dictates that Gibbons would first have to resign his position as governor in order for Krolicki to appoint him to the U.S. Senate. Surely Gibbons and Krolicki have already gamed this scenario.

The only stumbling block is that pesky Ensign. Does he have any plans to step down? Or a last roll of the dice?

Sally Denton is a writer based in Santa Fe, New Mexico, and author of six books, including T he Money and the Power: The Making of Las Vegas and Its Hold on America and the forthcoming The Pink Lady: The Many Lives of Helen Gahagan Douglas (Bloomsbury Press).