So the latest Muhlenberg tracking poll suggests that Joe Sestak is now 5 points ahead of Arlen Specter in the Senate Democratic run. Even factoring in the margin of error and so on, that's a big shift from just a week ago, when Sestak surprised everyone by being a mere 4 points behind.

I'm still not sure I believe it. And while Nate Silver of 538.com seems to think it could be for real, he also points out that polling in primaries is pretty unreliable. In any case, the gap between Sestak and Specter is just half the size of the number of voters who haven't made up their minds.

But if you'd told me two weeks ago the race could be this close, I wouldn't have believed it. And if Sestak actually wins? It'll surprise just about everyone -- the Democratic establishment as well as pundits in old and new media alike. 

Consider, for example, this 2009 piece from pa2010.com, giving Sestak advice about how to conduct a successful campaign. Of the "6 keys to victory" commended to Sestak by veteran scribe Tom Ferrick, the candidate seems to have flaunted half of them.

Among other things, Ferrick advises Sestak not to hire family members to run his campaigns: "I hear they were chaotic affairs," Ferrick wrote last year. "It would be a huge mistake to put [relatives] in charge of this one." Ferrick also urged Sestak"to stop with the 40-minute answers to simple questions."

That's not bad advice, really. Sestak still employs relatives -- a fact which Specter has exploited in his own ads -- and others have noted that Sestak's campaign has been chaotic this time around too. What's more, I can say from first-hand experience that as recently as Friday, Sestak was answering questions at ... very ... great ... length.

But perhaps Sestak's most important move was to ignore another of Ferrick's suggestions, one which may prove less insightful:

"Sestak's instincts may be to marshal his media money for the final days of the campaign. That would be a mistake ... If Sestak doesn’t define himself with voters early, Specter will do it for him"

Others in the new media faulted Sestak for waiting so long as well. As I wrote here not long ago, even Markos Moulitsas -- an early champion of Sestak's -- thought the candidate had blown it by staying quiet for so long. At the time I was tempted to agree because, sure enough, Specter did try to define Sestak, by questioning his service record.

But I'm gonna hold to my later -- albeit very tentative -- observation that Specter somehow ended up playing directly into Sestak's hands with that ad. No doubt the ad told some voters "There are things you may not know about Joe Sestak" ... but it reminded everyone of what we've always known about Arlen Specter. To wit, that he'll do just about anything to hold onto his office -- and that he used to be allied with the party that made "swiftboating" a household word. 

By denouncing "Rove-style" tactics and the like, Sestak played this issue just right (again, despite some carping even from new media folks). It made him the victim of exactly the kind of attack that Democrats most loathed about Republicans. (The fact that John Kerry has backed Specter, and offered a sort-of defense for his tactics, won't matter, I don't think. If there's anything Democratic loyalists like less than Rove-style attacks, it's the Democratic candidates who let those tactics work.) 

And when Sestak's own attack ads -- including a brutally effective hit on Specter's party-flopping -- came out, they looked like reprisals for Specter's first-strike launch. Even if you know that Sestak was waiting for just the perfect moment to launch these things, and would have done so no matter what Specter did. 

In retrospect, maybe it shouldn't have been a surprise that Sestak waited so long to make his move. Sestak, after all, hired Neil Oxman as a political consulatant. Oxman worked on the successful mayoral campaign of Philadelphia's Michael Nutter -- and a key component of Oxman's strategy was not going up early. As one representative account notes, "Nutter’s campaign was strategic, holding its ads until the seven weeks before the election and then buying airtime consistently until the end. One newspaper headline said of his victory: 'A perfect storm of ads, timing, issues fuels Nutter win in Philly.'"

Of course, it doesn't take Karl Rove to craft a strategy of keeping your powder dry until the closing days of an election. Voters often don't start paying attention until then anyway, and you don't want to run out of money in the final stretch. But it took guts for Sestak to remain so quiet ... and he got lucky too.

Specter's ad might well have torpedoed his campaign, just as Ferrick feared. In fact, if the Rove tactics don't work this time, I suspect it will be largely because Rove himself has already used them, tainting them with a political agenda that many Democratic voters abhor. (And let's not forget, they didn't work for Rove here either, since John Kerry won Pennsylvania.)

It's still possible that Sestak could lose, and lose badly. It's an axiom that no one counts out Arlen Specter. If that happens, well, I guess all Sestak's detractors will be proven right. And even if Sestak does win the primary, he's got a long road to hoe. This primary is a referendum on Arlen Specter, as most election contests involving incubments are. But a general election battle with presumptive Republican nominee will have a whole different feel, and Toomey seems smart enough to avoid Specter's missteps. And even if Specter blows himself up with his attacks on Sestak's service, Toomey may reap the benefits. The Philadelphia Inquirer, for one, seems intent on making Sestak's service record an issue. 

Too, if Sestak wins next week., some of the problems Ferrick last year noted will still be an issue. And it'll be interesting to see how Sestak will adjust to representing a party whose leaders have taken such strong positions against him.

But all that said, even if Sestak loses next week, well ... he's made it a closer than the last Democrat to go against Specter. And if Sestak wins, he'll have done so in defiance of his party elders, and a lot of the punditocracy who has been counting him out from Day 1. He'll have overturned mountains of conventional wisdom. Whatever misgivings you might feel about November, you'd have to feel pretty good about that.