If I believe this hard enough, will it come true?

Nate Silver: 5 Reasons Democrats Could Beat the Polls and Hold the House

Short story: polls that call landlines but not cellphones understate Democratic support by about 4 percentage points. Robocall polls are also biased in favor of more committed voters, which this year means Republicans. Gallup polls have a screwy methodology that is biased against less committed voters as well. Democrats have better turnout operations. And all those indicators of Republican strength (strength in generic poll, individual races, among different demographics, etc.) are all correlated and poll-dependent, so if the polls are wrong the deeper analysis is wrong as well. All of these things could - repeat could - mean Democrats don't do as badly as expected. But as Nate says, odds are the expectations are correct. Still, one can dream...