Well, not to be on contrarian, but Gore lost by running one of the most mixed up and passive campaigns ever.  

I'm not sure moving the right, or flip-floping really hurt Gore.

The press did a stunning hit job on Gore, remember "I invented the Internet" which HE NEVER said....Remember the whole "Color scheme"  thing.

What was STUNNING was, it was so clear BUSH had nothing to offer, except a change from the CLinton Era.  I think, in any other year, Gore wins.

He didn't lose his left base, but those who voted for Nader weren't ones he lost during the campaign by shifting the right, they were dissastisfied coming INTO the campaign.

Even so, Gore lost by not getting enough cross-overs and independents IMHO.