On the increasingly polarized political map, Pennsylvania's Eighth District is a true swing district.

Covering Bucks County and part of Montgomery, its voters stick to the middle of the road. They tend to be conservative fiscally, but skew slightly left on social issues, according to pollsters. They sent a Republican to Congress in 2004, voted Democratic in the next two House elections, and turned back to the GOP in 2010.

National observers have listed this year's contest as one of the top House races in the country, and it is widely expected to be one of the few close fights in the Philadelphia area.

So who is running in this oasis of moderates? A radical liberal and a tea party reactionary.

At least those are the choices if you believe the two campaigns, which have used the early stages of their race to slap each other with extremist labels and portray themselves as adherents to the sensible middle ground.

To Democrats, incumbent U.S. Rep. Mike Fitzpatrick is in a class with the hard-line right and Todd Akin, the Missouri Republican who introduced the phrase "legitimate rape" into the political lexicon. The liberal San Francisco SuperPAC CREDO named him one of the "Tea Party 10" it is campaigning against this year, calling him "The Ultimate Embarrassment" on its website.

Republicans, meanwhile, have labeled challenger Kathy Boockvar "Radical Kathy" with a website casting her as an "activist lawyer on the fringe of the left."

The Tumblr site includes a harried image of Boockvar (plucked from one of her own campaign videos) surrounded by photos of rioters smashing windows, a burning fire, and police wrestling with a protester whose long dreadlocks practically flail off the screen.

It's unclear where or when the pictures came from, or what connection they might have to Boockvar or the Eighth District. But subtlety isn't the point.

"The campaigns paint a clear picture of who they think the voters are," said Christopher Borick, a political scientist at Muhlenberg College. "The Eighth is very moderate, very middle of the road, and if you can effectively paint your opponent as being more extreme . . . you're hoping to cash in on that very moderate nature."

A similar dynamic is expected to play out in several House races in the Philadelphia suburbs, where voters tend to hew to the center and candidates have to follow rather than play to their base, as others do in more sharply partisan districts.

With both sides in the Eighth District well-funded, the stage is set for accusations, caricatures, and attempts to stoke outrage.

Democrats have made Fitzpatrick one of their top targets as they try to retake the House, or at least narrow the GOP's 50-seat majority.

Boockvar has raised $673,000 in campaign cash, roughly four times what the typical challenger has brought in, according to the Center for Responsive Politics. Fitzpatrick has taken in $1.8 million.

His experience as a Bucks County commissioner and U.S. representative - he was sent to the House in 2004, lost in 2006, and returned in 2010 - could help and hurt.

Fitzpatrick, 49, is known to Bucks voters, so molding opinions of him may be difficult.

Boockvar, who ran for a Commonwealth Court seat last year, is a relative unknown, leaving room for Republicans to define her.

On the other hand, Fitzpatrick has a concrete voting record, and Democrats have dug through it. As Congress tilted rightward the last two years, Fitzpatrick joined the GOP majority on several key votes that have become campaign flash points.

"His most recent run in Congress has followed his party more to the right, opening himself up to some of those claims," Borick said.

"I would hope the candidates keep the debates to the issues and encourage both campaigns and anyone else involved to do the same," Fitzpatrick said. Citing his voting record, he added, "I'm an independent voice for an independent district."

According to the website OpenCongress, Fitzpatrick broke with GOP leadership on 18 percent of his votes in the current session, sixth-most among House Republicans. And though he has courted and received support from the Independence Hall Tea Party, the conservative Club for Growth gave Fitzpatrick a 43 percent score on its priorities, among the lowest for Republican House freshmen.

Democrats argue that inside the percentages, though, are votes for key pieces of a right-wing agenda. Fitzpatrick voted to repeal President Obama's health-care overhaul and back Paul Ryan's budget, which would increase tax breaks, largely for the wealthy and corporations, slash spending on programs for the poor, and, most controversially, overhaul Medicare.

"I voted to secure Medicare for today's seniors and to strengthen it for the future," Fitzpatrick said, adding that Boockvar would side with Nancy Pelosi, the Democratic leader in the House, to "raid" Medicare. He pushed back against criticism that Ryan's plan would cost future seniors thousands of dollars, saying the savings would preserve the program.

Boockvar also cited Fitzpatrick's votes to strip funding from Planned Parenthood and his cosponsorship of a bill restricting federal funding for abortion. Its original version allowed an exception for "forcible rape," a term that pro-choice groups said was an attempt to narrow the definition of rape and limit allowances for abortions. Republicans said that wasn't their intention and dropped the word forcible.

"I don't care about the numbers or the percentages," Boockvar, 43, said. "I want to look at the substance. . . . He's voted the wrong way on every issue that matters for women."

The Democratic Congressional Campaign Committee launched robocalls last week comparing Fitzpatrick to Akin, trying to tie the Bucks representative to the Missouri Senate candidate.

"I completely disagree with Mr. Akin's statement," Fitzpatrick said. He opposes abortion but believes in exceptions in cases of rape, incest, and when the mother's life is in danger.

He cited a National Journal analysis that listed him as one of the least conservative Republicans in the House, a label the incumbent said bespeaks his independence.

"I eschew labels," he said when asked about the sparring between the two sides. "I don't see them as particularly helpful as voters are reviewing candidates."

Of course, the National Republican Campaign Committee has no such qualms.

Its "Radical Kathy" site describes Boockvar as "defending ACORN" - the controversial community group - and trying to "help felons vote." Fitzpatrick, asked about the site in light of his disdain for labels, said "they're not created nor maintained by my campaign in any way."

"It's classic Mike Fitzpatrick and the national Republican Party," Boockvar said. "They can't defend their own record so all they can do is call me names."

Republicans cite a friend-of-the-court brief she filed opposing a GOP effort to clamp down on ACORN's voter registration work.

Boockvar, a voter-rights attorney, said she "never represented ACORN, period."

Her work on that issue and others she said, was for a civil rights organization and was intended to make sure we enforce our voting-rights laws so that every eligible voter has the right and opportunity to vote."

On one topic, the candidates agreed: Each said the campaign's focus should be on jobs.

"I want to see people get back to work by supporting pro-growth policies, including a simplified tax code," Fitzpatrick said.

"The people don't want to be distracted by smoke and mirrors," Boockvar said. "They want to be talking about jobs and health care and Medicare."

The smoke is already thick, though, and it shows no sign of clearing.