*(Via NY Times) – Americans are usually forgiving when they vote a man into the White House and he wants a second term. Of the last eight elected presidents, all but two – George H. W. Bush and Jimmy Carter – got their four more years.

Which is why the conventional wisdom long held that Barack Obama would most likely weather his mid-presidency slump to win another term.

Then came the debt-ceiling debates of July and August, which seemed to crystallize Obama’s vulnerabilities in a way that even the Democrats’ midterm disaster of 2010 did not.

It’s probably because he handled the situation so poorly, simultaneously managing to annoy his base, frustrate swing voters, concede a major policy victory to Republicans and – through the fear imported into the market by the brinksmanship in Congress and the credit-rating downgrade that followed – further imperil the economic recovery.

On Aug. 12, a week and a half after the debate ended in Congress, Obama’s stock on Intrade, a popular political betting market, dipped below 50 percent for the first time. It has hovered just below the 50 percent threshold, usually at about 48 percent, ever since.

Read/learn more of this story by Nate Silver at NY Times.com.