With Pennsylvania’s Democratic presidential primary on tap for tomorrow, all attention has been focused on the relative strengths and weaknesses of Hillary Clinton–the consensus front-runner in the state, who needs as large a win as possible–and Barack Obama, who once appeared poised for an upset win that could have more or less ended the nomination contest.
But there’s been a secondary “story” in the Keystone State which may or may not have an impact on the Democratic outcome, but will definitely matter in November: a big surge in new Democratic voter registrations accompanied by another big surge in re-registrations into the Democratic column.
Jeanne Cummings has a good write-up of the phenomenon for The Politico. Here are her main findings:

According to the Secretary of State’s office, since January about 217,000 new voters have registered for the April 22 primary, the vast majority of whom signed up as Democrats….
That statewide Democratic surge has been accompanied by a flood of party-switching. More than 178,000 voters have changed their party status since January — and the Democrats have captured 92 percent of those voters.

Cummings quotes some speculation that this accretion of new Democratic voters–which is especially heavy in the Philadelphia area and in college towns–could help Obama outperform poll ratings tomorrow. But she really focuses on the possibility that we are witnessing “an ongoing partisan shift in Pennsylvania that could soon move it out of the battleground presidential states and ripple across congressional races this fall, as well.” That’s particularly true if you view the current spike in party-switching as a continuation of the realignment begun by Ed Rendell’s 2002 gubernatorial campaign, which arguably contributed to the big Democratic wins in the state in 2006.