McGovern lost in '72 as the ideologically pure liberal to run for president for the Democratic Party. He lost every state except one: Massachusetts. Somehow, the Democrats had decided in '72 that the country was an anti-war, nearly socialist country, and sent McGovern off to slay the Nixon dragon. Nixon won by about a two to one ratio.
Now, some conservatives seem to think that the country is a Tea Party, Evangelical nation, and they want the hardest core right winger that they can find. I think he is unelectable, fortunately.
The last two presidents ran as centrists (and each ended up being amazingly polarizing). Bush was "a uniter, not a divider", and Obama was "post-partisan." I believe the country is even more hungry for a pragmatic, non-ideological leadership than before, and now is hardly the time for a "divider, not a uniter" like Perry to be elected.
I was pretty sure, in 2008, when Obama won the presidency, that the Republicans would do what out of power parties always do - over-react to their loss and decide that the reason they lost was that they weren't being ideologically pure enough, so they would nominate a true blue extremist from their party. Perry certainly seems to fit that bill.
He has one positive, however, he seems to speak from the heart. I have long observed that when presidents are replaced, the people vote for someone who is strong where the incumbent is seen to be weak. The low character of Nixon was replaced by the perceived high moral character of Carter; the weak willed Carter was replaced by the confident Reagan; the out of touch H.W. Bush was replaced by the "feel your pain" Clinton; the vacillating Clinton/Gore was replaced by the decisive W. Bush; the close minded W/McCain was replaced by the open minded Obama. Now, Obama's perceived weakness is his lack of engagement and emotional distance from the problems of the country. When he speaks, he speaks like a professor discussing political theory. What little I've heard of Perry, he speaks very viscerally, from the heart and from the gut.
But, this is not a Tea Party nation, and he will go down pretty hard, I believe. It will be interesting to see if the Republicans fall for the ideological purity trap.