Most polling suggests she cannot win the general election. Most polling also suggested Ronald Reagan could not win the general election in 1980. A fundamental difference was that Palin has 95% name recognition right now and Reagan was far from that recognition in 1980, even though he’d run in the 1976 primary against Ford.
If Palin gets in, she is going to have to work very, very hard to rehabilitate her image among not just independent voters, but also — and I think this is key — conservative Republican voters who long ago gave up on the dream of a Palin 2012 candidacy and moved on. Many of those voters have signed on to other campaigns.
While Palin fans may assure themselves that those former Palin supporters would come home quickly, I don’t yet see any evidence for that and think, at least initially, Palin would drag down everyone except MItt Romney.