With no significant evidence of progress in Iraq, why are poll numbers up for whether we made the right decision to invade? Here’s a New York Times Week in Review article on the puzzle:

The Times and CBS News conducted a poll from July 9 to July 17 with 1,554 adults, mostly about Hillary Clinton…

In the poll, The Times and CBS News posed a standard question that asks respondents to think back to the invasion. Specifically, the poll asked: “Looking back, do you think the United States did the right thing in taking military action against Iraq, or should the United States have stayed out?”

Forty-two percent of those polled said the United States did the right thing, and 54 percent said the United States should have stayed out of Iraq. The last time the question was asked, in May, 35 percent said taking military action against Iraq was the right thing and 61 percent said the United States should have stayed out.

The July numbers represented a change. It was counterintuitive. None of the other war-related questions showed change. Mr. Bush’s approval rating had not changed. Nor had approval of his handling of Iraq. The level of support for Mr. Bush’s decision to send more troops to Iraq — the “surge” — was about the same as it had been in past polls. Support for the decision to go to war had risen modestly and nothing else in the poll could explain it.

A Newsweek poll conducted July 11-12 had a similar finding for the same question. But the magazine had not asked its question since December, so it is hard to know whether its current reading measured any recent change.

…When the second round of results came back, the numbers were nearly identical to the ones found in the poll about Mrs. Clinton. In the poll conducted last weekend with 889 adults, 42 percent of the respondents said the United States did the right thing in taking military action against Iraq, and 51 percent said the United States should have stayed out.

There was also a drop in the number of people who said the war was going badly. In the latest poll, 66 percent of Americans said things were going badly for the United States in its efforts to bring stability and order to Iraq. That is down from 76 percent who said the same thing in May.

Here is a plot of the “right decision” numbers over time, which shows that Republicans, Democrats and independents all ticked upward:

I can’t come up with a convincing explanation — can you? (One possibility, of course, is that it’s a statistical artifact, but the fact that three polls have all shown an increase for the same question suggests that it’s not.)