what will happen to john kerry?

[Erc]

If he had lost in a Gore-esque fashion, he might have considered an '08 run.  As it stands, he's got less of a chance than Carol Mosely-Braun.

He'll probably stay in the Senate, I'd assume.  Whether he'll call it quits in '08...I don't know.

[Erc]

Past unsuccessful Presidential Candidates and their later (elective) political careers:

Al Gore:  nothing
Bob Dole:  nothing

Michael Dukakis:  Served out remaining two years of his term as Governor of Massachusetts.  Did not run for elective office thereafter.

Walter Mondale:  Ran for Minnesota Senate, 2002.  Lost.

George McGovern:  Served out remaining two years of his Senate term.  Won re-election, 1974.  Lost re-election bid, 1980.  Failed in his bid for nomination of the Democratic Party in the 1984 Presidential race.

Hubert Humphrey:  Ran for Senate, 1970.  Won.  Won re-election to the Senate, 1976.  Died in office.

Barry Goldwater:  Ran for Senate, 1968.  Won.  Won re-election to the Senate, 1974, 1980, 1984.  Retired, 1987.

Adlai Stevenson:  No elective offices

Thomas Dewey:  Re-elected as Governor of New York, 1946, 1950.

Wendell Wilkie:  Never held elective office, before or after.

Alf Landon:  Lived another 50 years, but did not hold another elective office (to my knowledge)

Al Smith:  Nothing.

John W. Davis:  Nothing

Bob LaFollette:  Served out his Senate term until his death.

and so forth...