House Speaker Nancy Pelosi is proving to be the Republicans' favorite election-year villain -- and a nightmare for some centrist Democrats who are struggling to survive politically.

The GOP's "Fire Pelosi 2010 Bus Tour" is in its third week of roaming the country, stopping for rallies in key congressional districts. Republican-inspired ads in closely contested congressional districts paint Pelosi as a stone-faced, Republican-hating promoter of big government and big liberalism. Some moderate Democrats are running ads distancing themselves from her and are openly questioning whether she should lead them next year.

"She's such an easy target," said Brad Coker, the managing director at Mason-Dixon Polling & Research, which surveys states nationwide.

It's hardly unusual in nonpresidential years for one party to demonize the other side's congressional leaders: Republicans mocked House Speaker Tip O'Neill, D-Mass., in 1982, and Democrats tried the same tactic in 1998 with House Speaker Newt Gingrich, R-Ga.

However, they were the most visible, powerful figures in their parties in election years when the president was from the rival party. This year, President Obama and Pelosi are both Democrats, as is Senate Majority Leader Harry Reid of Nevada.

So why is Pelosi the Republican target of choice?

Because "she has become the face of what everybody doesn't like about Congress," said Scott Jennings, the deputy political director for President George W. Bush and now a Louisville, Ky., GOP strategist.

Pelosi, who's been the speaker of the House since 2007, has employed some highly visible hardball partisan tactics to get controversial measures approved. In the past 21 months, she's muscled through bills that overhauled the nation's health care system, provided $814 billion in economic stimulus, revamped the financial regulatory system and attempted to restrain global warming.

The very qualities that make her a strong speaker -- decisiveness, hardball partisanship and her willingness to impose tough discipline on her members -- often don't play well during election campaigns, when voters want more empathy and civility.

"She's getting a lot of the blame because of her manner," said David Dittman, a political consultant based in Anchorage, Alaska.

Some criticism of Pelosi may be calculated to appeal to those who resent women rising to positions of authority formerly reserved to men, but at least one analyst said she's a lightning rod more for her ideology than her sex.

"Her problem is she's seen as a San Francisco liberal," said Darrell West, the director of governance studies at the Brookings Institution, a center-left research center. Her trouble, West said, is not so much that she's a woman as "it could be that she has a problem being a liberal woman. Conservatives have no problem with conservative women," such as former Alaska Gov. Sarah Palin and several prominent Republican female candidates in this year's elections, he noted. "Gender is less important to them than ideology."

Pelosi also fits conveniently into the Republican message that government is too big and liberals are running wild. Pelosi, Obama and Reid represent the "nexus of liberalism," said Sal Russo, the Sacramento, Calif.-based political consultant behind the Tea Party Express, which has helped boost several conservative GOP candidates this year.

Pelosi dismisses the Republican campaign against her as little more than standard partisan rhetoric and says that moderate Democrats' reservations about her leadership are nothing new.