WHEN NONSENSE SPREADS LIKE A CANCER…. House Speaker John Boehner (R-Ohio) and House Majority Leader Eric Cantor (R-Va.) will go to great lengths to avoid denouncing birther lunacy. This may have something to do with their reluctance.

Birthers make a majority among those voters who say they’re likely to participate in a Republican primary next year. 51% say they don’t think Barack Obama was born in the United States to just 28% who firmly believe that he was and 21% who are unsure. The GOP birther majority is a new development. The last time PPP tested this question nationally, in August of 2009, only 44% of Republicans said they thought Obama was born outside the country while 36% said that he definitely was born in the United States. If anything birtherism is on the rise.

In other words, the Republican fringe is no longer the fringe. We now have a poll showing a majority of GOP primary voters accepting a ridiculous conspiracy as fact. The same poll found that just 28% of these Republicans accept reality.

The split, such as it is, within GOP primary voters leads to interesting divisions. Public Policy Polling found that the more deeply confused these Republicans are, the more likely they are to like Sarah Palin, Newt Gingrich, and Mike Huckabee.

And given that this poll suggests most primary voters are, in fact, birthers, candidates hoping to run sane campaigns will be at a disadvantage in the coming months.

All of this, of course, comes against a backdrop in which Republican state legislators in nearly a dozen states are already pushing birther legislation.

It’s quite a political party the GOP has put together, isn’t it?

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.