Tomorrow's rain forecast could spell trouble for some candidates. The question is, who?

An article in The Hill suggests rain could favor an Obama victory in North Carolina, where the heaviest rain is expected to fall near the more-conservative coast.

Generally, however, rain dampens turnout among Democrats, according to a study published in 2007. The study found that rain lowers turnout by about 1 percent per inch of rainfall, to the detriment of Democrats, and may have contributed to Electoral College totals in 1960 and 2000.

An earlier study, which examined fewer election years, held otherwise.

Another factor to consider might be the effects of early voting. Any rain-related turnout reduction may still not be enough to counter the large Democratic turnout during early voting.