I think the worst to VP choices would probably be the two who cost the ticket the election.
Bob Dole probably cost Ford the election because mondale beat him soundly in the debate (at least that is what i heard). People were kinda uncomfortable with him being the number two guy during a time when the republican party was so scandal filled (Agnew and Nixon had to resign FOR COMPLETELY DIFFERENT REASONS).
A slightly better choice but still bad would be Lieberman. If Gore had picked Graham of Florida, we would be currently picking a republican challenger to president gore. I personally think that the 'confederate flag flyers' that Dean talked about probably couldn't swallow a Jewish man as Vice-President and most of them who might have though about voting for Gore did not. And if just 1000 of such souls voting for Gore in Florida would make him president.
The guy who's name begins with an 'E', the original McGovern pick, was prettu bad....even though McGovern would probably have lost anyway... 
There are worse men picked to be vice president; men that should never be president. However when the man at the top doesn't have a chance it doesn't matter, to a degree, who he picks as his running mate. No one cares who Nader's running mate was in 2000 or who it will be in 2004 since there is no chance that Nader will become president. But Ford and Gore as stand alone men had over a 50% of election. So it context their choice of a running mate who is much much worse because the running mate hurt them enough to cause them to lose.
