The Concord Monitor provides a brief look at veterans in U.S. politics throughout the years.  Some facts they've compiled:

--Since the draft ended in 1973, U.S. citizens serving in the military fell to 1% of the population.
--31 of the 42 presidents were veterans.
--The 2008 election could mark the first time since World War II that a veteran isn't on the final ballot (if McCain doesn't make it).
--In the generation from 1870 to World War I, it really did matter if a campaigning candidate had fought in the Civil War.

The article goes on to look at whether military experience really does impact how a political leader conducts a war.  There was James Madison (civilian) who was in charge during the War of 1812 when the White House burned:

"It was really an active question about whether civilian presidents were capable of leading America in wars and managing the military in wars...[Madison] failing badly - that set a poor first example."

But, then there was Lincoln (civilian):

"Abraham Lincoln, he had been in the Black Hawk War for a couple of months and he had been a critic," Birkner said. "And yet he proved to be an adept commander-in-chief, a very patient and effective leader on the military side."

Eisenhower (veteran):

"The typical voter seeing America stuck in the morass of Korea, they thought, 'If this guy could do D-Day, he can do Korea,' " said Birkner. "And he did. He didn't deliver a victory, but he delivered peace with honor."

And then there's this view: