Two of these three sentences say it all. From Slate, on why he's not the Dem's best chance, regardless of whether he is the country's.
There are lots of other reasons that Gore probably shouldn't run, often articulated by inside-the-beltway types. A lot of Democrats still have sour feelings about a nominee who blew a winnable election. Gore never liked the day-to-day work of politics (as opposed to governing) and was a lousy campaigner.emphasis mine