A burgeoning field of presidential hopefuls.

• Position: YOUR LIFE

With the ultra-early announcements that Sens. Hillary Clinton (D.-N.Y.) and Sam Brownback (R.-Kan.) and former New Mexico Gov. Bill Richardson have taken major steps toward becoming presidential candidates for 2008--and let's not forget former New York City Mayor Rudy Giuliani or Sen. Barack Obama (D.-Ill.)--the upcoming election (although almost two years away) already is approaching one of the largest fields of contenders ever.

One reason why so many hats are being tossed into the ring so early is this is a rare occasion when no incumbent president or vice president is running, explains John Aldrich, professor of political science at Duke University, Durham, N.C., and coauthor of Change and Continuity in the 2004 and 2006 Elections.

"If the president is up for renomination, his party will either have an entirely uncontested nomination, such as George W+ Bush in 2004 and Bill Clinton in 1996, or a very restricted field, like when Gerald Ford was challenged by Ronald Reagan in 1976 and Jimmy Carter was challenged by Edward Kennedy and Jerry Brown in 1980," Aldrich says. "When the incumbent vice president runs, he is the dominant figure, usually winning the nomination, often early in the contest, like Al Gore in 2000 and George Bush the elder in 1988.

"As a result, fewer challenge such a strong contender. In all other cases, there will certainly be candidates seen as relatively strong, as Sens. Clinton and [John] McCain [R.-Ariz.] are seen for 2008, but they will not be seen as strong as an incumbent president or even vice president."

Aldrich points out that the last time both parties had open...