Republicans would likely obtain a filibuster proof majority if the entire Senate were up for grabs in November, according to a little-noticed post by Nate Silver, one of the nation's premier polling experts.

Silver, writing on his blog at The New York Times, said the reason that Democrats are poised to lose the House and not the Senate is that only a third of the Senate is up for re-election at any given time. His musing reflects just how bad the election season is for Democrats this year.

"The reason that Democrats are likely to hold the Senate but not the House — the necessary and sufficient reason — is because only one-third of the Senate is up for re-election every year," Silver wrote. "If the whole Senate were up for re-election, Democrats would lose it and lose it badly."

Silver says that Republicans might even have achieved a veto-proof majority (67 senators) if all of the Senate was in play.

Take a look at our Senate forecast map. There’s a lot of red there. Part of that, yes, is because Republicans tend to do better in the middle of the country where the states are physically larger — but that kind of misses the point.

Right now, among the 37 Senate elections, we have Republicans favored in 25, Democrats favored in 11, and one other (Colorado) that’s too close to call. If Democrats have a relatively good election night, they will win about one-third of the available Senate races. And if anything, the states that are voting for Senate this year are slightly blue-leaning. If the entire Senate were up for re-election in this political climate, the Republicans would be favored to earn a filibuster-proof majority, and might even earn a veto-proof majority! Fortunately for Democrats, that’s not how the system works. (Maybe some of our readers could go though the list of 63 Senators that are not up for re-election and guess which ones they’d expect to lose if they were. It could be kind of fun.)

Democrats are expected to lose the House of Representatives, which is sure to derail Democrats' legislative priorities.

"Democrats are performing about on par in each chamber, losing most (although not all) swing districts, some (although certainly not most) blue-leaning districts, and almost all (although not absolutely all) red-leaning districts," Silver adds.

"Now, this is not to suggest that Republicans don’t have some 'candidate quality' problems in the Senate," Silver continues. "They do. I think you can argue, for instance, that Generic Republican should beat Generic Democrat in a state like Colorado in a political climate like this one, when in fact the race is about tied there between the actual candidates. Generic Republican would probably also be favored over Generic Democrat in Nevada, and would almost certainly be favored over the non-generic (and very unpopular) Harry Reid, but the race is very tight there too. Even in Kentucky, which Rand Paul seems likely to win, the race would probably not be within 5 or 6 points in an environment like this one had the Republicans picked a more orthodox nominee."