First, you need to add G W Bush to the "elected only once list."
Second, you left off FDR who was elected FOUR times and people still love the guy.
Third, why will four years of Barak Obama cause a negative legacy that will be linked to the Dems for generations but the legacy of GW will be forgotten by 2012? What about the legacy of Richard Nixon? He was a crooK!
This post is psuedo-history. Ken citing a bunch of real people to appear to make a point that doesn't correlate to the data at all.
The answer is two. What is your point?
So that would mean three Dems have won twice in the last 150 years, although it seems like FDR should count either two or three times depending on how you look at it.
For Republicans it would be, lets see, six, if you accept Bush won twice or that Nixon's cheating counts.