The left has been honestly disappointed in Mr. Obama. He did not come through as they think he should have in myriad ways—the public option, closing Guantanamo, war, now the tax plan. But—and this makes it all more complicated and fascinating—the left does not say Mr. Obama has been revealed to be at heart a conservative, or a Republican. Most of them know he is one of them—his worldview is more of less theirs, his assumptions are theirs. Does anyone doubt he would have included a public option in health care if he thought he could have? He judged that he couldn’t. He didn’t have the numbers in the Senate. It isn’t an argument about philosophy or ideology. It’s only an argument about what’s practical and possible.

Some on the left argue that if only the president had talked more, and more passionately, if he’d worked it harder, he could have brought the country to support leftist programs. But why do they think this? The general public has seen the president out there for two years talking and promoting a generally leftist direction. Voters demonstrated in elections through 2009 and ’10 that a generally leftist direction is not what they want.

All of this—the disenchantment of the left, the confusion of the party’s professionals—has led to increased talk of a primary challenger to Mr. Obama in 2012.

And here too the president’s position would be without parallel.