The Financial Bailout

[Jack]

"I have asked this on other forums, and haven't received a response. Does anybody know if an Senator or Representative incumbent has to go through a primary election?"
Fabs, the answer to that is: maybe
Any time an incumbent is challenged within his own party by another candidate, there will be a primary. That doesn't happen often, admittedly, because unless the incumbent has some serious problems, the party (whichever he belongs to) will support the incumbent.
But, it does happen. A recent example would be Joe Leiberman in Connecticut being challenged in the Democratic party senate race in 2006. Leiberman lost the Democratic party nomination, ran as an independent, and won the Senate race.
Usually, primary races within a party take place when the party is out of office, or the incumbent retires.