The Republicans in the House impeached him. The Linguini-spined Democrats in the Senate refused to convict. Because of their cowardice (or because Bill had something on them), Al Gore was NOT the incumbent President going into the 2000 elections. (The same Al who said he would have done things differently in Florida with Elian Gonzalez if he had been President!)
So, the cowardly Democrats denied Al BOTH the incumbency and the chance to improve his standing in Florida, either one of which would have undoubtedly tipped the race in his favor.
You have only gutless Democrats to thank for why Al's campaign slogan wasn't : Re-Elect President Al Gore!