In the long-run, it's impossible to predict what an Obama administration would do for the electoral prospects of his fellow Illinois Democrats. But in the short-run, a boost is all but guaranteed. With the presidential nominee generating excitement in his homestate -- and progressive organizers working hard to reach new voters in diverse communities -- new registrations have soared:

Illinois election workers are digging out from under a record number of last-minute voter registrations.

All-time highs have been set in St. Clair County near St. Louis and in Cook and Lake counties near Chicago. The city of Chicago's voting district is close to setting a new record of more than 4.5 million voters, officials said.

And the numbers are sure to climb higher: Officials are still processing registrations and people still have two weeks to sign up to vote.

Cook County saw the biggest jump, adding 60,000 people since Oct. 1 alone. In Lake County, 28,000 people have registered since the primaries. Will County's rolls have increased by more than 30,000 over that same stretch. Given the registration campaigns directed at young voters and underrpesented communities, broader voter identification trends favoring Democrats, and Obama's popularity in the region -- an October SurveyUSA poll found Obama leading McCain in the 10th Congressional District 62-36 percent, for example -- it's very likely the majority of new registrants are Democrats.

What's that mean down-ballot? The AP takes a guess:

The Illinois senator could bring enough new Democratic-leaning voters to the polls to make a difference in tight legislative or congressional races. His campaign also makes it easier for other Democrats to identify potential donors and volunteers -- someone who requests an Obama yard sign, for instance, could be asked to support other Democrats, too.

For more on the potential "Obama effect," check out my feature on young Illinois progressives and our post from May.