The FiveThirtyEight forecast for Sunday gives Barack Obama a 69.4 percent chance of winning the Electoral College on Nov. 6. That’s essentially unchanged from Saturday — although there have been some modest shifts back and forth in the numbers over the course of the past two weeks since Mitt Romney named Representative Paul D. Ryan of Wisconsin as his vice-presidential nominee.

Mr. Romney was given a 28.0 percent chance of winning the Electoral College on Aug. 10, the day before he officially announced Mr. Ryan as his pick. The forecast then moved somewhat toward Mr. Romney after a series of improved polling in swing states for the newly minted Republican ticket, achieving a peak of 33.3 percent on Wednesday. It has since receded slightly to 30.6 percent, however, as Mr. Obama held leads in a number of swing state polls late last week.

These shifts could be consistent with a small vice-presidential “bounce” for Mr. Romney which has since faded — perhaps as less favorable stories for Republicans, like the comments on abortion and rape made by Representative Todd Akin of Missouri, have come to dominate the news cycle.

But these are only very minor differences — the model estimates that Mr. Romney gained a net of perhaps one percentage point in the popular vote after his selection of Mr. Ryan, and has lost perhaps half a percentage point since then. Changes of that magnitude could potentially be caused by statistical noise, as well as by real shifts of opinion.

What’s clearer is that Mr. Romney did not get as large a bounce in the polls from his vice-presidential pick as most past candidates have — a fact that can arguably be read as a bearish sign for him.

The Republicans do seem to have made some headway in Mr. Ryan’s native state of Wisconsin, however. And their last few polls in Florida have been been reasonably strong, defying the conventional wisdom that suggested Mr. Ryan’s views on entitlement programs could be damaging among the senior population in that state.

Can Romney Achieve Focus in Tampa?

Political coverage over most of the past two months has veered between hard news events like the Supreme Court’s ruling on Mr. Obama’s health care bill, and a set of personal issues that can occupy the news cycle for days at a time, like Mr. Romney’s tax returns or the comments made by Mr. Akin.

Both campaigns also seem to have been in trench-warfare mentality, with a focus on day-to-day tactics rather than long-term strategy.

The Republican convention in Tampa could represent an opportunity for Mr. Romney to break through the noise and show some more sustained improvement in his polling. Conventions almost always do produce bounces in the polls. These bounces fade, but an especially large or an especially small bounce can be an indicator of how the rest of the race is likely to proceed.

However, the Republicans face an unusual pair of challenges at their convention: first, that the interval separating the Republican convention from the Democratic one in Charlotte is extremely short; and second, that the news media’s attention could be divided between the developments in Tampa and those in the Gulf of Mexico, where Hurricane Isaac is a threat to New Orleans and other cities on the Gulf Coast.

Sunday’s Polls

The only new state poll out on Sunday was in Ohio, where the Columbus Dispatch published a poll showing Mr. Obama and Mr. Romney tied at 45 percent each.

The Columbus Dispatch poll is unusual: It is conducted entirely by mail, with surveys sent out to a random selection of Ohio voters.

The potential problem with this polling method is that because returning a mail survey requires more effort than taking a phone call, the response rates are likely to be lower and could potentially overrate the strength of the candidate with the more enthusiastic supporters.

However, it might be noted that all forms of survey research — certainly including telephone polling — face a problem of low response rates. And historically, the performance of the Columbus Dispatch poll has been about average, with some strong years and some poor ones.

If its survey differed greatly from the consensus, I would be a little wary of it — but showing a tie in Ohio is not that different from the average of surveys there, which puts Mr. Obama ahead but by a narrow margin. In short, I don’t have any problem including Dispatch’s survey alongside the rest of the Ohio polls. Mr. Romney’s chances of winning Ohio improved slightly in our forecast as a result of the poll, increasing to 33 percent from 31 percent on Saturday.

Mr. Romney got slightly unfavorable results in the national polls that were out on Sunday, however, with the Rasmussen Reports tracking poll showing Mr. Obama pulling into a 2-point lead among likely voters — a better result than it appears for Mr. Obama since Rasmussen’s polls have been somewhat Republican-leaning this cycle.

There was also a poll of likely voters from the Tarrance Group, a well-respected Republican polling firm, which gave Mr. Obama a 1-point lead among likely voters.