At FiveThirtyEight, Nate Silver has published his first official Senate forecast of the year, and it gives Democrats some good news:

[T]he odds of a favorable overall outcome for Democrats have increased in recent weeks. The forecast model now gives them a 70 percent chance of controlling the chamber, either by having at least 50 seats and the presidency, or 51 without it.

Although this represents the first official FiveThirtyEight forecast for the Senate this year, I ran backdated forecasts to July 1 based on the polls that were available at that time. Two weeks ago, for example, the model would have given Democrats a 52 percent chance of retaining Senate control — and four weeks ago, it would have given them a 39 percent chance.

The trend toward Democrats is a relatively recent one. Part of the shift may reflect the bounce President Obama received from the Democratic convention. If so, it could recede, especially if Mr. Obama’s poll numbers do so, too.

But our analysis also suggests that the Democratic advantage has probably been building over the past few weeks, and may not have any one root cause. Instead, Republicans risk death by a thousand cuts, with a gradual deterioration in their standing in several important races, and their inability to field optimal candidates in others.

As Nate’s last graph indicates, it’s a complicated landscape, so you should read the whole thing. But factors boosting Democratic prospects include the Missouri fiasco, strong recent poll showings by Sherrod Brown, Bill Nelson and Elizabeth Warren, and the strong winds behind the candidacies of Martin Heinrich in NM and Mazie Hirono in HI.

Democrats still have reason to worry about the last-minute deployment of 501(c)(4) and Super-PAC funds in selected races. But the situation for them looks a lot better than it did at this point last year, when they were looking down the barrel of big disadvantage in vulnerable seats.

Ed Kilgore

Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.