Two recent polls show Democratic Senate candidate, Joe Sestak, closing the gap and even leading his Republican opponent, Pat Toomey. Will Pennsylvania, once a probable GOP pickup this season, elude Republicans again?

Public Policy Polling released a controversial poll Tuesday showing Sestak leading Toomey by one point. That poll was a comparative outlier and provoked a bit of a backlash because it had sampled more Democrats than came out to vote in 2008 – unarguably a benchmark year for Democratic turnout.

The poll was met with some skepticism from the poll-watching community. However, Morning Call released a poll Wednesday with a more realistic sample that confirms a comeback for Sestak. In that poll, Sestak leads Toomey by three points, 44 to 41 percent. This is perfectly consistent with a recent Democratic internal poll conducted by Garin-Hart-Yang Research Group (October 8-10) which showed Sestak up 3 points, 47 to 44 percent.

Is this accountable to a natural tightening with the state’s majority of Democratic voters suddenly tuning in? Is it bad polling? Or is it just Joe Sestak? Historical data supports Sestak’s propensity for a comebacks at this stage in the campaign. In his 2006 campaign for the House seat in Pennsylvania’s 7th district Sestak trailed his opponent, incumbent Republican Rep. Curt Weldon, significantly up to October. A September 13, 2006 Public Opinion Strategies poll showed Weldon leading Sestak by 19 points. Sestak went on to win that race by 15 points.

A more recent metric for measuring Sestak’s propensity for comebacks is the Pennsylvania Democratic primary on May 18 of this year. Then, Joe Sestak faced former Republican-turned-Democratic incumbent Senator, Arlen Specter. Sestak trailed in every poll taken in that race, even into early May. The final RCP average of polls in that race showed Sestak with a slight 3.2 percent lead over Specter – Sestak would go on to win that race by 8 points.

Deirdre Murphy, the DSCC’s National Press Secretary, attributes at least some of the recent tightening of the polls in Pennsylvania to the Sestak campaign’s focus on Pat Toomey’s record and his history as a derivatives trader. “Democrats are aggressively making sure Pennsylvania voters know Pat Toomey’s record as a Wall Street derivatives trader whose pro-China, anti-Pennsylvania polices do nothing to help middle class families in the state.”

The Democratic party has invested heavily in keeping holding Pennsylvania’s Senate seat for Democrats. A recent estimate showed that DSCC purchases in that state by November 2nd could total over $9 million. The DSCC has most recently come out with an effective ad criticizing Toomey’s close ties to a Chinese billionaire.

NRSC went up on the air early last week following a significant $3.4 million media purchase in the state. However, a number of 501(c)(3) groups have been advertising for Toomey in that state since the Democratic primary. The DSCC is quick to highlight that this pro-Democratic movement in the polls has been occurring amidst significant media purchases and positioning by pro-Republican groups.

The Keystone state is not the only place where statewide races have been tightening. In Kentucky, the Senate race between Attorney General Jack Conway and physician Rand Paul has been closing fast. Similarly, Senate races in California and Washington which have been oscillating are now 50/50 tossups. Senate races in Illinois, West Virginia and Nevada have been, and remain, nail-bitingly close in the polls – rarely does any candidate in these races poll outside the margin of error.

The Real Clear Politics average of polls, as of Wednesday, shows no less than 8 tossup Senate races. Given the trends in these races, they are likely to stay outside of either party’s column until election night—perhaps even later.

Noah Rothman is the online editor at C&E. Email him at nrothman@campaignsandelections.com