Regardless how good President G.W.Bush's poll numbers look now, I believe Gore will run again. I do not think Gore believes President Bush is unbeatable, especially considering that we're talking 2004. Politically speaking, 2004 is a long ways away.
Don't just ascribe this to massive total population growth.
Remember, that 1986 amnesty for illegal aliens - after Reagan's reelection - brought hordes of people to citizenship and eligibility to vote. And most all of them would vote Democrat.
Klinton and Bush Daddy - and later Klinton and Dole - would split the vote with Ross Perot, the first really serious independent candidate since 1968's Wallace candidacy, which long predated Reagan's election.
In 2000, Algore similarly benefited from substantial elements of nonminority voters defecting from Bush to vote Buchanan. It's a safe bet none defected from Algore to vote Buchanan.
ALGORE IN HIS OWN WORDS, 1992-2000 - including Earth In The Balance!