Jon Lieber, head of Eurasia Group's coverage of political and policy developments in Washington, DC shares his perspective on US politics.

What is polling telling us three weeks before the midterm elections?

Public opinion polling is taking election watchers on quite an exciting ride this year, from showing Republicans with a massive advantage early in the year, to demonstrating a surge and support for Democrats over the summer. Most election watchers think that surge is fading now in the final weeks before the election. But today, we wanted to focus on a few numbers that matter for forecasting the election results.

But first is the generic congressional ballot, which asks voters which party they would prefer to vote for in an upcoming election. If you have to look at one indicator to make a forecast about congressional elections in the US, this is it. Particularly in the House of Representatives. This indicator has shown Republicans with an unusual advantage for most of this year, which they lost over the summer as abortion climbed in importance for voters. While Democrats lead in this indicator right now by about half a percentage point, because of the way districts are drawn, they would need to have a several-point lead in order to be thought of as favorites in taking the House. So this is telling us that the general environment is good for Republicans at the moment.