Last week I argued that the first presidential debate made it possible for the first time to really imagine what Mitt Romney might be like as president. Apparently a number of Americans are imagining it—and, for the first time it seems, not entirely minding the idea.

In multiple major polls released so far this week, Romney has taken a lead over the president. He's up by four points in the Pew Research poll, and up by two points in polls by Gallup and Investors Business Daily. Somewhat ironically, Rasmussen, which many commentators frequently accuse of leaning GOP in its findings, shows Romney and the president tied.

Overall, the new polls are enough to give Romney his first ever lead in the RealClearPolitics polling average.

Yes, at just 0.7 points, Romney's lead is still a small one. But the only two polls in the RCP average that still show Obama in the lead were taken entirely or mostly prior to the debate. Which suggests that Romney's lead may actually be larger. At minimum, the momentum is now clearly in Romney's favor.

Whether that will matter much by election time is harder to say. As polling guru Nate Silver points out in The New York Times, historically the most important factor in predicting the outcome of a presidential election is still the economy, and the economic fundamentals, mediocre as they are, still mildly favor President Obama. But for now the polls are pretty clearly headed in Romney's direction.