But sure enough, a new Public Policy Polling survey released today has the two candidates virtually tied.

The main reason, says PPP, is that Pennsylvania’s sizable Democratic base, which enjoys nearly a one million vote registration advantage over Republicans, appears to finally be waking up:

Democratic voters are getting more engaged as election day moves closer. Barack Obama won Pennsylvania by 10 points in 2008 but our August survey in the state found those planning to vote in November had actually supported John McCain by a point in 2008, suggesting a massive drop off in Democratic turnout. Now those saying they will vote next month supported Obama by 4 points in 2008. The enthusiasm gap is still there but it’s not as severe a problem for Democrats as it was 2 months ago.

Of course, many of those Obama voters are now not so sure about their choice: 51% of Pennsylvania voters disapprove of the job the president is doing, while only 43% approve. That makes Sestak’s climb that much tougher, but he’s been making real strides among independent voters since August as well. Whether this is because independent voters are taking to Sestak or simply becoming more familiar with some of Toomey’s more extreme views, he’s polling better than most Democrats among this group as well, according to PPP.

Naysayers will call the poll as an outlier, but it will likely generate much-needed enthusiasm among Democrats in the state. And having followed Sestak around on the campaign trail during his primary run, I can testify to the fact that the man is tireless and seems to possess the magical ability to finish strong in a long and grueling race.

The first — and most surprising — item concerns Gov. Joe Manchin (D-W.Va.), who a new Public Policy Polling survey shows trailing his GOP opponent John Raese 46 percent to 43 percent in the race to fill the late Sen. Robert Byrd’s (D-W.Va.) Senate seat. Just months before, soon after Manchin signaled his intention to run, most preliminary polls put him up by at least 20 points, but since then his lead has steadily diminished. The poll results are also coming out at the same time as revelations that a federal probe into highways built in West Virginia is being focused, at least in part, on a $150 million road that connects I-79 to to Fairmont, Manchin’s hometown — but any connection to the governor’s office at this stage is circumstantial at best.

Meanwhile, new polls showing former Rep. Pat Toomey (R-Pa.) holding a steady 7 point lead over Rep. Joe Sestak (D-Pa.) in the race to replace Sen. Arlen Specter (D-Pa.) are causing come forecasters to recategorize it from “toss up” to “lean Republican.” But anyone who followed Sestak’s come-from-behind victory over Specter in the primary knows it’s too soon to say anything for sure: “Pat Toomey is in a good place, ahead by 7 points with six weeks to go. But Congressman Joe Sestak has proven himself a tough competitor so it’s too early to order the champagne,” Peter Brown, assistant director of the Quinnipiac University Polling Institute, said in a statement.

Finally, a new CNN/Time/Opinion Research poll indicates that Sen. Michael Bennet (D-Colo.) is falling behind Weld County DA and tea party–backed candidate, Ken Buck, in Colorado’s Senate race. The difference in the race seems to be all about the enthusiasm gap that’s plaguing Democrats around the country, pundits note: Buck leads Bennet 49 percent to 44 percent among likely voters. When registered voters are polled, however, Bennet takes 47 percent to Buck’s 44 percent. Getting those 2008 Obama voters out to the polls for Bennet, in other words, is a must-do if he hopes to keep his seat.

At least Democrats can still be thankful that Christine O’Donnell is the GOP Senate candidate in Delaware.

The two most closely watched races will be in Delaware and in New Hampshire. In Delaware, tea party Senate candidate Christine O’Donnell looked to be stumbling in her race against Rep. Mike Castle (R-Del.) before getting some important endorsements and even more important polling numbers this weekend. In New Hampshire, long time GOP favorite Kelly Ayotte is facing some heat from attorney Ovide Lamontagne, who snagged an endorsement from tea party celeb Sen. Jim DeMint (R-S.C.) last week.

The story for November is the same in both races: Castle and Ayotte look like easy favorites to win their respective Senate seats, while O’Donnell and Lamontagne would turn the races into toss ups, at best, pushing the Republicans that much further away  from capturing the Senate.

The primaries — which are also taking place in Maryland, Massachusetts, New York, Rhode Island, Wisconsin, and the District of Columbia — feature tea party candidates on the GOP primary ballot in New York and Wisconsin as well, prompting the Wall Street Journal to question whether the whole insurgent movement is working out so well for Republicans after all:

Mississippi Gov. Haley Barbour, chairman of the GOP’s gubernatorial campaign committee, said the party will benefit from keeping the tea party within its ranks.

“It would have been far, far, far worse if tea party candidates had decided to run as independents,” he told reporters last week. “I hope they would continue in the next cycle to run as Republicans, and I believe they will, because I believe the evidence is clear that they got a fair shake. They were welcomed and they participated, and in some places won primaries.”

The tea party movement has clearly played a big role in generating the “enthusiasm gap” between Republicans and Democrats — one of the primary factors that pollsters have been pointing ominously towards when they make predictions about big Republican gains in the fall. But then there are the numerous times that the movement has propelled fringe candidates who might ultimately hurt their party’s chances to the forefront — candidates like today’s New York GOP gubernatorial hopeful Carl Paladino:

In New York, some Republicans give Carl Paladino, a real-estate millionaire, little chance of winning the governor’s race if he beats former Rep. Rick Lazio for the GOP nomination. Mr. Paladino’s self-funding campaign has gained attention for his denunciations of both political parties and for such proposals as using empty prisons to train welfare recipients and the unemployed in new job skills and “personal hygiene.”

“The concern is that Paladino, because of his past statements, will be characterized as being not ready to be governor,” said John Faso, the last Republican nominee for governor in New York. “If Republicans are sullied or embarrassed by a candidate at the top of the ticket, then you could adversely affect turnout.”

This entire lead is within the margin of error, so by the poll’s own (flimsy) standard, the candidates are statistically tied.

Don’t expect that basic fact to ruin a breathless headline, though. Even when they do reflect statistically significant gaps, national polls are often misleading, because they trump up shifts in the electorate that have little impact on the election. A huge spike in Obama’s support in California, for example, does nothing for him in November.

There is, however, one potentially significant trend in this new poll. After all the delegation breakfasts and convention speeches ended, it appears that McCain shored up his party base more than Obama. That’s not surprising. McCain defined his convention by letting the base override his own preferences for a running mate. Ditching Gov. Ridge for Gov. Palin unleashed a multi-day abortion-bashing, media-sniping puritan political orgy. Let There Be Palin, he said, and The Base said it was good.

Since then, McCain’s support among Republicans jumped 8 points, according to the CBS/NYT poll. In the same period, Obama only gained four points among Democrats.

So while both nominees held exactly 79 percent support among their respective parties before the conventions, McCain has now consolidated his base a bit more.

All the national poll caveats still apply, but this has more electoral impact because battleground states with a Republican edge are more likely to firm up for McCain. See Florida, for example, which is now slipping away even though Obama is spending more there, and despite his campaign’s attempt to woo older voters there with trips by both Clintons.

The larger race is still clearly trending Obama’s way. The economy hurts McCain in Ohio, while mortgages hurt him in the Southwest swing states that he must hold for victory, especially Nevada, which led the country in foreclosures this fall. So while the “fundamentals” of his base constituency are strong, the rest of the electorate is still eyeing change.

Update: Commenter “Total” writes: “That’s not what margin of error means. First off, Obama’s up 5 and the margin of error is 3, so it’s not within the margin of error.” Wrong. The margin of error is plus or minus 3, for a spread of six. Thus The Times reports that Obama’s apparent lead is “a difference within the poll’s margin of sampling error.” Total also recommends an analysis by Kevin Drum that stresses how these figures essentially turn on probability, so the “bigger the lead, the more likely that someone is ahead” — even if they are technically within the margin of error. We agree on that one.