GOP presidential candidate Mitt Romney has had his best week of the campaign. Going into the first debate last Wednesday, the Romney poll numbers both nationally and in key states had slightly improved from the nadir in the weeks following the release of the Florida fundraising tape with his “47% comment.” He trailed nationally by between 4 points (RCP average) and 6 points (Nate Silver’s model) entering the debate, and was behind in every key battleground state except North Carolina, which was even.

Today, he has pulled almost even in the RCP national poll average  after a shocking poll from Pew put him into a 4 point lead over President Obama, and cut the lead in Nate Silver’s poll to 2.5%. Bettors on Intrade now give Romney a 37% chance of victory, double what it was a week ago.

The last time the Pew poll was conducted, Obama led by 8% — meaning there has been a 12% shift in the Pew results. Romney showed even larger gains among women voters in this survey, and he took a lead in the Midwest, home to many of the key battleground state races: Ohio, Iowa, Wisconsin, and now maybe Michigan. In Nate Silver’s’ model, the Pew poll on its own lifted Romney’s chances of winning the White House by almost 4%.

Polls have been more volatile the last month than they were in 2008 at this stage. John McCain shot out to a brief lead in early September after the GOP convention, only to quickly fall 6 to 7 points behind after the financial crisis hit that month following the Lehman Brothers collapse and the Wall Street bailout bill making its way through Congress. McCain never made a dent into the lead after that.

This year, the GOP convention provided a much smaller bounce for Romney, which was wiped out by a larger lift to the Obama campaign from its convention — most of it due to a well-received nominating speech by Bill Clinton. Some of this convention bounce appeared to be fading when the 47% tape was released by the grandson of Jimmy Carter and Mother Jones magazine. Romney’s numbers nosedived, falling into the low 40s in some polls, and Obama opened up big leads in key states — particularly Ohio, a state that has been part of every winning GOP presidential campaign since the Republican Party was founded.

Now, following a smashing victory in the first debate (about three-quarters of those surveyed thought Romney won), he has closed the gap everywhere, and in some surveys moved into the lead in key states.

The vice presidential debate is on Thursday night, and while Joe Biden can be expected to be more engaged than Obama was last week, the Romney campaign is hopeful that the momentum it has gained this week can be carried forward with a strong performance by Ryan. The debate is likely to be livelier and nastier than the presidential debate, with more attacks by the vice president than were offered by Obama, who for the most part appeared to be coasting in the first debate.

The best news for Mitt Romney this week was in the state polls. Romney is narrowly ahead in the last two surveys in Florida. He is ahead in two of the last three surveys in Virginia. He is up 1 and down 1 in the last two surveys in Ohio. He is even or trailing very narrowly in Colorado and Nevada.

The biggest surprises are in Wisconsin, Michigan, and Pennsylvania. All three states seemed to have disappeared from Romney’s target map in September, with Obama moving up to double-digit leads in surveys in all three states. This week, two new polls showed Obama ahead by 3% in Michigan, two new polls showed him up 2% and 3% in Pennsylvania, and a new poll by Democratic-leaning pollster PPP had Obama up only 2% in Wisconsin.