While certainly it would end the phenomenon of swing states, it would only replace it with swing districts---those involving the largest cities, such as New York, L.A., Chicago, Detroit, Dallas.... guess who gets the lion's share of the new "swing city" vote?
You suggested that Gore would have won in 2000 if Colorado had proportional voting, a similar but not identical scheme. However, who would have won if all states (not just Colorado) used proportional voting?
That wasn't me that suggested it. But I think it's likely that Gore would have won if all the states used proportional allocation. He did, after all, win the popular vote.
Mmm. If the electors are split according to congressional districts, one vote per district, the 2000 map by district indicates a GWB landslide.
http://www.polidata.org/maps/prcd021r.htm
Just my guess, the Dem districts in urban areas vote overwhelmingly Dem (70-80%?)compared to a closer vote most Pubby districts and that gave Gore the big 'popular' vote number. It didn't give him the majority of congressional districts. Good thing for him NY and CA are winner take all or he never would have been close.