I have often heard it said that being a Senator is a good stepping stone to President of the USA. Research shows this to be really false, and that's bad news for Kerry. Oh, many sitting senators run for President, but for over 120 years, they have rarely and barely won.
The one exception that proves the rule is John F. Kennedy, the only sitting senator of the modern political era to be elected President. And barely so -- there are many who still say JFK stole the election, and in any event it was one of the closest in history before Bush/Gore. JFK was also a congressman, and he sat out a few years of his Senate career due to back problems.
Before Kennedy we have to go back 84 years, and out of the modern era, to Warren Harding, who won handily from the Senatem then died in office. And before that you go to Benjamin Harrison, who lost the popular vote but won the electoral vote.
The first century of U.S. history has many Senator->President transitions, which may have created this myth.
Some suggest that the reason is that a Senator has a long voting record which can be used against him or her, and that does appear to be the case. But the suggestion it's a good stepping stone is false.
(Also worth noting that Kennedy, Harding and Harrison did not defeat sitting Presidents. Defeating sitting Presidents is of course hard to do, but Carter and Clinton, who did it, were both Governors.) I didn't research enough to find out how far back you have to go to find a Senator unseating the President.Here's another strange statistic I noticed. Each time we have had a son or grandson of a President (Bush, Adams, Harrison) the junior has won the electoral college but not won the popular vote. In fact, the electoral college reversal of the popular vote has only happened one time when it wasn't a dynasty president, with Rutherford B. Hayes.