One thing to consider -- no matter how polarized Democrats and Replublicans get, is it possible that elections are actually decided by those voters who go to the polls and have no idea what the issues or candidates' positions are? Is that why you see all those campaign ads, street signs and commercial TV smear campaigns?
Maybe elections are more about sound bytes and name recognition (and who can sneak in the more effective attack ad) than it is about true governing philosophy or policy positions. It would explain a lot!