"supports" works. Also, "endorses". More colloquially, "stumps for".
Millard Fillmore.
Joseph Biden , the incumbent is running for another term as VP.
This event occurred in 1944 when FDR was elected.
Millard Fillmore.
"undecided voters" is one common term for these people.
"undecided voters" is one common term for these people.
Abraham Lincoln ran for president with Andrew Johnson as the Vice Presidential candidate. This would be Lincoln's second term as president, having chosen a new vice-presidential candidate.
Franklin D. Roosevelt was elected to a 4th term in 1944. He died in office in 1945.
The last time a Republican candidate won the popular vote in a presidential election was in 2004, when George W. Bush was re-elected for a second term.
Obama was elected in 2008 to a four-year term which ends on January 20, 2013. He is expected to be a candidate for a second term in 2012.
Perhaps "balancing the ticket" is the term you are looking for. If the presidential candidate is closely identified with one faction within the party or one geographical area, the VP candidate can be chosen from the other faction or a different region and so try to offer something for everybody.
If this should happen, the electoral college would most likely cast their votes for the vice-presidential candidate of the dead winning candidate.