I didn't say he was incorrect. It's clearly less important than winning the election, and it's not really a sign of trends in the direction of democrats. The fact that Bush did better in almost every state in the country in the next election shows this. You also saw a big drop in support for Obama from 2008 to 2012. If there was an ongoing shift to the left we'd have seen Bush lose in 2004 and Obama win big last year.
I didn't say that you said that he was incorrect. I suggest that you pull the chain on this one before we divide by zero.
It's not "clearly less important" than winning the election if we are talking about party popularity, which is the subject as near as I can tell. Bush only barely carried Florida, he couldn't have done worse without losing. The 2004 election was against a different opponent, and as an incumbent president.
I'd say that it's likely that the differential between 2008/2012 can also be partially attributed to things like McCain vs. Romney, Sarah Palin, Bush hangover leaving Republicans home, the 2008 election not being representative of Obama's real support due to the financial crisis and "first AA president" thing... and this is just what I came up with off the top of my head. Never mind that Obama is one of the most centrist leftists we've had in a while, and GWB wasn't much of a conservative.
No, there are just all kinds of problems with your implications.