Primaries and caucuses show parties' vital signs.

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The primaries and caucuses tell Americans more than just who will be running for president, indicates a professor of political science from Purdue University, West Lafayette, Ind. 'qhe underappreciated feature of our presidential nomination system is the turnout question," explains James McCann.

"In many states, people who participate in the primaries and caucuses do not have to be registered with a specific party, so, based on who is going to the polls, you can infer some things about the health and popularity of the parties."

Many commentators have remarked on how the presidential contests of 2008 differ from 2004, but the better comparisons are 2000 and 1988, when there was no incumbent president seeking reelection, McCann relates. In 2000, the 88,000 Republicans in the Iowa caucus outnumbered the 60,000 Democrats, he points out. This year in Iowa, 240,000 Democrats participated in that state compared to 120,000 Republicans.

"There is an increase...