People have exceedingly short memories.

How quickly they forget.

It’s instructive to compare Mr. Obama’s rhetorical stance on the economy with that of Ronald Reagan. It’s often forgotten now, but unemployment actually soared after Reagan’s 1981 tax cut. Reagan, however, had a ready answer for critics: everything going wrong was the result of the failed policies of the past. In effect, Reagan spent his first few years in office continuing to run against Jimmy Carter.

Mr. Obama could have done the same — with, I’d argue, considerably more justice. He could have pointed out, repeatedly, that the continuing troubles of America’s economy are the result of a financial crisis that developed under the Bush administration, and was at least in part the result of the Bush administration’s refusal to regulate the banks.

But he didn’t. Maybe he still dreams of bridging the partisan divide; maybe he fears the ire of pundits who consider blaming your predecessor for current problems uncouth — if you’re a Democrat. (It’s O.K. if you’re a Republican.) Whatever the reason, Mr. Obama has allowed the public to forget, with remarkable speed, that the economy’s troubles didn’t start on his watch.

Big mistake.