Senate Democratic leaders, stung by their recent inability to gain the filibuster-proof majority needed to pass financial reform or an extension of unemployment benefits, have begun blaming tea party influence for intimidating Republican moderates like Susan Collins and Olympia Snowe of Maine.

"It’s getting increasingly difficult," Senate Majority Whip Dick Durbin (D-IL) said of the attempt to win over GOP moderates. "And I think Maine is going through its own transformation and challenge within the Republican Party. And I think that’s a factor."

Snowe downplayed Durbin's comments, telling Politico, "I think that Sen. Durbin shouldn’t ascribe political motivations." She instead blamed "gamesmanship" for her part in the impasse over extending unemployment benefits and tax incentives.

According to Politico, "The Maine Republican Party has moved fiercely to the right with a new [platform] backed by tea partiers, and GOP voters nominated a gubernatorial candidate who emerged as a tea party favorite. More pressing for Snowe, however, is that some conservative activists want to find a primary challenger to run against her in 2012."

Politico notes that Snowe "is already being targeted by tea party groups in her state that cite her support for an early version of Democratic health care legislation and her decision to vote for the $787 billion stimulus."

The last-minute reluctance of Snowe, Collins, and Senator Scott Brown of Massachusetts to vote for financial regulation reform that they had previously supported -- citing their opposition to a provision for a tax on banks to pay for the new regulations -- has struck some observers as particularly inexplicable.

"While it's almost cliché for Republicans to complain about new taxes, in this case it's rather bizarre," noted The Atlantic's Daniel Indiviglio. "They must have known that this bill would involve additional government spending. So where did these Senators expect this money to come from when they voted for the bill initially?"

Another Republican moderate who has recently been rebuffing the Democrats is Senatoir Lisa Murkowski, who is facing a tea party-backed challenger in next month's Alaska primary. Murkowski backed a cap-and-trade energy bill in 2007 but has now reversed that stance.

Murkowski's opponent, Joe Miller, is a climate change denier who has demanded that other candidates "reject the argument that man made CO2 emissions are causing significant global warming." He accuses Murkowski of taking "a very liberal stance on most of the issues" and she has fought back by emphasizing "all the measures I have voted against and have objected to."

"Last session the state legislature passed two joint resolutions opposing federal cap and trade legislation and the EPA's power grab on carbon emissions, which mirrors what I have been fighting in Congress," Murkowski stated in a press release this week. "These measures -- and other efforts like it -- bolstered my efforts to fight for Alaska in Washington."