Nate Silver: The Momentum Mirage

538 on the battle for the Senate and the media coverage:

You might be hearing that Democrats or Republicans have “momentum” heading into the final week of the 2014 campaign. On Tuesday, for example, a Washington Post headline asserted “Midterm momentum belongs to GOP.” That was based on a generic ballot poll showing a 6 percentage point Republican lead. But later in the day, a Fox News generic ballot poll came out showing Democrats up by 1 point instead — Fox had previously shown Republicans ahead.

This pattern — or rather, this lack of a pattern — has been typical throughout this election cycle. Whenever one party seems to be gaining an advantage, the other party has countered it with some good news of their own.

Republicans have maintained a narrow overall edge in their quest for a Senate majority, but the magnitude of their advantage hasn’t changed much throughout the campaign. When the FiveThirtyEight model launched Sept. 2, it gave Republicans a 64 percent chance of winning Senate control. In our latest forecast, their chances are 62 percent. They’ve never been higher than 66 percent or lower than 53 percent.

Just a reminder.