To truly appreciate the increasingly rightward tilt of the GOP – courtesy of tea-party pressure; or, just as importantly, the threat of tea-party pressure – consider the recent behavior of Senator Olympia Snowe, the reputed moderate from Maine. She is clearly peering over her shoulder, in the hopes of heading off any right-wing threat to her job in 2012.Back in the fall of 2009, Snowe was the only Republican senator to vote Yes at any stage of the process for any version of health care reform; she did so in the Senate Finance Committee, voting to advance the historic bill that requires Americans to buy insurance (better known as the “individual mandate”). And she declared: “When history calls, history calls. I happen to think that the consequences of inaction dictate the urgency of Congress taking every opportunity to demonstrate its capacity to solve the monumental issues of our time.”But shortly before Thanksgiving of 2010, Snowe announced that she has added her name to a pending lawsuit, filed in federal court in Florida, that seeks to knock out the underpinnings of health care reform by scrapping the individual mandate. In other words, she initially voted for reform – including the mandate, which is fundamentally crucial to the workings of reform – but now she wants the courts to gut reform because she finds the mandate to be “imperious and intrusive.”Granted, Snowe did vote against the final health reform package, and she did state at the time that she had serious qualms about requiring Americans to buy insurance (she was mostly worried about affordability, as opposed to the lawsuit’s questioning of the mandate’s constitutionality). But there is a difference between a soft stance and a hard stance. The soft stance would be to stay silent and let the various lawsuits proceed. But by signing her name to the federal lawsuit in Florida (thereby joining 29 other Republican senators), she has taken a proactive hard stance and publicly signaled that she now wishes to undo all that has been done to solve what she only recently called “one of the monumental issues of our time.”So why the hard turn toward the right? Take a wild guess. With all deliberate speed, she needs to dump her reputation for moderation and polish some conservative creds.A Maine tea-party official, Ian Dodge, said earlier this month that Snowe is in the crosshairs for 2012: “There is going to be a primary, and she is going to have at least one tea-party candidate against her. If it is done correctly, she can be beaten. She is definitely the next target.” The tea partiers feel emboldened up there, having just elected an outspoken conservative in the gubernatorial race, a guy who has vowed to tell President Obama to “go to hell,” so they figure it’s an opportune time to purge someone who in her 16 senatorial years has committed the cardinal sin of occasionally working with Democrats.Snowe actually identified this intra-Republican trend back in April ’09; in a guest newspaper column, she lamented “the shrinking of our ideological confines,” and wrote that “being a Republican moderate sometimes feels like being a cast member of Survivor – you are presented with multiple challenges, and you often get the distinct feeling that you’re no longer welcome in the tribe.”But to be a survivor, to feel welcome in the tribe, she is apparently prepared to adopt the new tribal rites; hence, the cornerstone of health reform is “imperious and intrusive.” As if any conciliatory moves will sway the Maine tea-partiers. They’ll remember her initial Finance Committee vote, as well as her vote in favor of economic stumulus. They’ll put up a primary challenger no matter what she says or does now. (Although they’d be wise not to coalesce around a loon. In 2010, laughable tea-party nominees may well have cost the GOP Senate seats in Delaware, Colorado, and Nevada. And the electorate in 2012, a presidential year, will be more politically diverse than the midterm electorate of 2010.)The bottom line is that Snowe, and the ever-dwindling roster of Republican moderates, are feeling that tea-party undertow. The mere threat of an uprising on their right flank is now enough to compel them to hew to the new orthodoxy – yet another factor that makes congressional compromise exceedingly difficult. (Just as the Democrats are dealing with increasing complaints on their left.) Snowe can ill afford to behave anymore in the tradition of independent-minded Maine women, such as the late moderate senator Margaret Chase Smith. If she wants to keep her job, she has to party down with the ascendent tea crowd. As she said last year, in another context, when “history calls, history calls.”——-In my latest Sunday newspaper column, which was timed for the holiday weekend, I listed all that I was thankful for. And I easily could have added Dick Lugar, the veteran Republican senator from Indiana, who on paper is also vulnerable to a tea-party primary challenge in 2012 – but who insists that “I will continue to be Dick Lugar,” which is his genteel way of telling the wingers to take a hike. Lugar didn’t vote for health care reform, or economic stimulus, but no matter, the tea-partiers in Indiana want him out anyway. As one spokeswoman said the other day, “We think the climate is right for it, and we believe it is a must.”I’m thankful for Dick Lugar because of something he said last week. As the GOP’s foremost expert on nuclear proliferation (a specialty he has honed for decades), he’s trying to get his colleagues to support ratification of New START, an arms reduction pact with the Russians that builds on previous bipartisan pacts endorsed by Ronald Reagan and George H. W. Bush. Here is what Lugar said to his Republican colleagues, most of whom are against the treaty largely because President Obama is for it:”Please do your duty for your country.”What a radical concept. That alone should guarantee Lugar a tea-party challenger in 2012.