Say, what has happened to Olympia Snowe lately?  The Senator from Maine has spent years cementing her reputation as one of the few moderates left in either party willing to cross the aisle to cut deals.  In the last two years, though, Politico notices a lot more party-line votes from Snowe amid rumors of a feud with Harry Reid.  Is she voting with James Inhofe on environmental legislation out of spite, fear — or common sense?

Snowe has been voting far more along Republican party lines as she faces the possibility of a tea party challenger in her 2012 Republican primary, making her a much less willing partner for Democrats in search of a Republican deal maker. Democrats also are targeting her seat in 2012, so Reid has less incentive to give her bipartisan cover.

Senators in both parties are starting to talk about the spat.

“I don’t think it’s smart,” South Dakota Sen. John Thune, No. 4 in Senate GOP leadership, told POLITICO, referring to the way Reid dealt with Snowe. “I don’t know if I get why of all people that you would want to hope you can appeal to in the future — Olympia would be someone like that.”

But according to Democrats, Snowe has lurched to the right and abandoned her moderate leanings. She surprised environmental activists earlier this year when she voted with Sen. Jim Inhofe (R-Okla.) and Senate Minority Leader Mitch McConnell (R-Ky.) to block environmental regulations on greenhouse gases. And she sided last month with just nine Republicans on a resolution by tea party favorite Sen. Rand Paul (R-Ky.) criticizing President Barack Obama’s policy on Libya.

Vote rankings this year show that she’s siding with her party 20 percent more often than she did in the previous Congress, meaning she has voted nine times out of 10 with a majority of her conference.

The “spat” apparently started with the ObamaCare bill, from which Reid excluded Snowe along with most of the other Republicans in the Senate.  Snowe had provided a key vote for Reid on the Porkulus bill despite Reid and Nancy Pelosi locking Republicans from drafting that bill as well.  Snowe’s voting record has tilted much more towards the GOP since then, which is why Politico speculates that Snowe is voting rightward out of spite with Reid — which has made Reid’s life a lot tougher in the past two years.

Of course, Snowe also faces a Tea Party challenge in next year’s primary for her re-election campaign.  After seeing the damage the Tea Party did to Republicans who vote like Democrats in office, Snowe may understandably want to provide herself some cover by aligning herself with people like Inhofe, especially on energy and environmental policy.  The change in her voting record appears to predate the enormous increase in enthusiasm among Tea Party activists, though, so that may be more of a secondary issue.

Politico leaves out a third possibility, though.  Snowe may want to pursue moderate approaches to policy, but this administration and the Democratic leadership in Congress over the last several years seems determined to push through radical expansions of federal power instead.  When even a well-known moderate has little choice but to resort to party-line votes, the problem may not be the moderate, but the radicals on the other side.