1 The vice-presidency doesn't count - per FDR's first VP, it's not worth a bucket of warm euphemism.  Also, the VP's only role is to act as a conditional senator for special tie-breaking and ceremonial purposes.  Thus, I'd classify Coolidge and T.R. as falling into the governors-class of presidents, with Taft being a special case because of his immediate experience as a serial colonial governor.  Truman, Nixon, and Johnson all get pitchforked into the senatorial claque, with Ford being the sole congressman in the list.  Bush the Elder was also a congressman, but he spent far more time as a bureaucratic functionary, and his governance style definitely reflected that mind-set.

That tends to clarify matters somewhat, but the currently favored conventional-wisdom truism that governors' experience prepares for the office while senatorial time-serving ruins a politician for it founders on the rather violent exceptions of Woodrow Wilson on the one hand, and Truman & Kennedy on the other. 

Furthermore, the side-theory that primarily non-governmental experience is worthless for the job is spun sideways by the twin contradictions of Hoover and Eisenhower. Hoover's primarily executive experience as the World's Humanitarian Fixer and Eisenhower's service life & apotheosis as Saviour of Europe produced wildly dissimilar White House careers.

I'm inclined to say that experience matters less than personality.  Wilson was a ferocious, bigoted, narrow-minded thug, and his single term of office as governor of New Jersey had little bearing on his performance as president.   Truman's time in the collegial Senate had little effect on his quietly combative personality and peculiar blend of tenacity and conditional flexibility.  I rather suspect that McCain, if elected, would have ended up a second Truman, but obviously Obama has proven to be no such creature.

2 Thanks Mitch.  I'll do a new version of the table in the morning with the VP column excised.  And always remember that Carter was the Governor of...  Someplace or other.

Truman was an interesting character; I'd like to learn more about him.

3

I don't agree with that. The VP has often been a springboard to national candidacy for the President, for instance Nixon in 1960 and Humphrey in 1968 and Mondale in 1984, not to mention Bush Sr. They generally haven't been very successful at it, but it's widely viewed as a gateway.

Ford, coming out of the House, is a huge exception because he was never elected to the presidency. After Agnew resigned, which wasn't related to Watergate but happened after it, everyone knew that the new VP which would be chosen (through processes of the 25th Amendment) had a damned good chance of becoming President either through Nixon's impeachment or his resignation.

So the leaders of both parties in both chambers went to Nixon and pretty much told him that the only candidate they'd accept was Ford. He was House Minority Leader and was widely respected by both sides.

So he finished Nixon's second term, but when he ran in 1976 he was defeated by Carter, meaning that he and Rockefeller are the only Pres/VP pair in the history of the nation to not have been elected to the offices. And God Willing, it'll never happen again.

4 As you can see, Senators seldom make it to the Presidency.  Most especially long serving Senators.  They have to make too many concessions while in office. Concessions put them at outs with their own party.  And most of them aren't "pretty" enough for the press to ignore what they have or haven't done while in the Senate.  Obama had a huge advantage as he did absolutely nothing while he was in the Senate. (the Illinois State Senate never counted since the press completely ignored the fact that he was ever there).

I always find it amusing when a current serving Senator gets up and starts a speech saying "elect me so I can get things changed"  - because being in the Senate would be the place to effect the most change.  The President only signs what Congress gets to his desk.

I think you're looking at it the wrong way - it would be more instructive to look at the number of Senators who have run for their party nomination and never made it. 

5 Or simply look at the record of the Senate, to test the hypothesis that senators make bad senators.

6 Lately that seems to be damn near a given - no matter who the Senator might be.  LOL.