"It's been a good week for Democrats in Pennsylvania. In between the last election in November and Monday's registration deadline,
more than 161,000 people have signed up as Democrats, the majority of whom were previously registered Republicans or independents. That surge has helped the party grow by 4 percent, and top 4 million members for the first time in state history.
"This is definitely going to help Obama," says Terry Madonna, a political science professor at Franklin & Marshall College. "The question is, how much?"
Obama has dominated open primaries over the last three months, and while Pennsylvania's is closed, his campaign made a major push to convert as many independents and Republicans as possible. For Obama supporters, the idea was to make the contest a de-facto open primary.
While efforts have been underway for months, they went into overdrive after the March 4 primaries made Pennsylvania's vote relevant. The Clinton campaign ran phone banks and registration tables as well, but the effort wasn't as coordinated as the opposition.
Terry Madonna says the surge of new Democrats will likely help Obama cut into Clinton's double-digit lead in the state, but it may not be enough to win there. "Arguably, [the new registrants are] are worth three to four percent of [Clinton's] total. I think that's a safe assumption," he says."
Campaigns and Elections' Politics Magazine