Idaho Senate Larry Craig is fast becoming the inconvenient truth of Capitol Hill. The senator who first said he would resign after pleading guilty to charges related to an alleged bathroom-sex solicitation and then said he was going to try and beat the rap and stay now seems to be intent upon remaining in the Senate indefinitely.

This creates a big political problem for Senate Republican leaders. Already facing the prospect of losing as many as a half dozen seats — in Maine, New Hampshire, Minnesota, Virginia, Colorado and Alaska — in a 2008 election cycle that is shaping up as their nightmare scenario, Senate Minority Leader Mitch McConnell and his compatriots are terrified that Craig will extend his stay for months.

Craig’s refusal to relinquish his grip on the Idaho seat creates trouble in that state, as it prevents Republican Governor Butch Otter from filling the vacancy with a Republican who would be set up to claim the seat in 2008. The longer the delay, the harder it is for Idaho Republicans — a notoriously contentious lot — to get their affairs in order and secure a seat that ought not be vulnerable.

But Idaho is not McConnell’s biggest concern. He and his aides are more worried that the sordid stories associated with Craig, as well as his continued presence in the GOP caucus, will further erode enthusiasm among evangelical Christians and social conservatives for the party’s candidates. The fear a scenario similar to the one that played out when Florida Congressman Mark Foley’s page-boy scandal highlighted hypocrisy in the GOP ranks shortly before the 2006 election.

The threat faced by McConnell — himself up for reelection in 2008 — is real. And so to is the threat they are now preparing to direct at Craig. According to the Washington Post, McConnell is “threatening to notch up the public humiliation” in order to force the Idaho senator to quickly quit. What does that mean? Republican strategists quietly acknowledge that McConnell is talking about ginning up an open-to-the-media ethics committee inquiry with full public hearings designed to examine the many allegations regarding Craig’s sexuality and sex life.

It’s a sleazy scenario, especially in a Senate that has traditionally kept such matters cloaked. But if it is openness that McConnell wants, perhaps the Senate Democratic majority should give it to him. The Craig inquiry could come right after the public hearings regarding the sexuality and sex life of Senator David Vitter, the Louisiana Republican and McConnell confidante whose penchant for patronizing prostitutes — an illegal act that some Republican stalwarts might even consider immoral — has been much in the news of late.

If Larry Craig’s bawdiness in bathrooms is worthy of an ethics investigation then, surely, an turn-the-TV-cameras-on inquiry regarding David Vitter’s frequenting of a house in New Orleans will help to usher in Mitch McConnell’s new era of openness.