Mitt Romney continues to show improved numbers in polls published since the presidential debate in Denver on Wednesday and has now made clear gains in the FiveThirtyEight forecast. The forecast gives him roughly a 20 percent chance of winning the Electoral College, up from about 15 percent before the debate. Mr. Romney’s gains in the polls have been sharp enough that he should continue to advance in the FiveThirtyEight forecast if he can maintain his numbers over the next couple of days.

Four of the five national polls published on Saturday showed improvement for Mr. Romney. In the Rasmussen Reports tracking poll, which conducted about two-thirds of its interviews after the debate, he went from a two-point deficit against Barack Obama to a two-point lead. Mr. Romney gained two points in the Gallup tracking poll, which now shows him down by three. He also gained roughly 1.5 percentage points in the RAND Corporation’s online tracking poll, reversing a gain that Mr. Obama had made on Friday. And a companion pair of polls published by Clarus Research Group just before and after the debate showed a five-point swing toward Mr. Romney. He trailed Mr. Obama by four points in a poll that Clarus Research Group conducted on Tuesday night, before the debate, but led him by one point in a poll they conducted on Thursday.

All of these national surveys except for the Clarus Research Group poll still contain some predebate interviews, meaning that they may underestimate the gains that Mr. Romney may eventually realize. This particularly holds for the Gallup and RAND Corporation tracking polls, which use seven-day filed periods; only about 30 percent of the interviews in those polls postdate the debate. In general, the surveys seem to be consistent with a universe in which Mr. Romney has been polling about evenly with Mr. Obama nationwide in interviews conducted after the debates.

There were few state polls published on Saturday, but a Gravis Marketing poll of Colorado also showed a sharp reversal toward Mr. Romney. He led in its newest survey, which was conducted on Thursday after the debate, by 3.5 percentage points. Although Gravis Marketing polls have had a very strong Republican lean so far this cycle, the trend in the poll is nevertheless extremely favorable for Mr. Romney, since he had trailed Mr. Obama by roughly five percentage points in a poll it conducted in September.

The only poll in which Mr. Romney failed to make gains on Saturday was in the online tracking poll published by Ipsos. That survey showed Mr. Obama holding onto a two-point lead among likely voters, the same as in the poll Ipsos published on Friday, although the numbers were still improved for Mr. Romney from the surveys it had been publishing before the debate.

If there is any silver lining for Mr. Obama in these data, it may be that polls of registered voters show a weaker trend toward Mr. Romney than polls of likely voters. He still leads Mr. Romney by six points in the version of the Ipsos poll among registered voters, for instance, and the Gallup tracking poll, which is conducted among registered rather than likely voters, has not shown an especially sharp shift toward Mr. Romney so far.

Why is this factor favorable for Mr. Obama? Because likely voter polls can be more sensitive than registered voter polls to temporary swings in voter enthusiasm, which sometimes reverse themselves as there are new developments in the news cycle.

More broadly, although it is clear that Mr. Romney has made gains, it is still too early to tell how long-lasting they might be. Many of the polls that showed the sharpest swing toward Mr. Romney were conducted on Thursday, immediately after the debate and on a very unfavorable day of news coverage for Mr. Obama, and will not yet reflect any change in voter sentiment from Friday morning’s favorable jobs report.

Still, as I wrote yesterday, my guess is that the forecast model is still being somewhat too conservative about accounting for the change in the environment. In a good number of the polls, Mr. Romney has not only improved his own standing but also taken voters away from Mr. Obama’s column, suggesting that he has peeled off some of Mr. Obama’s softer support in addition to gaining ground among undecided voters.