Controversial conservative and former Alabama chief justice Roy Moore won the Republican primary for the state's Senate seat on Sept. 26, setting up a crisis within the GOP. Here's a look at three problems his win poses for the D.C. establishment. (Jenny Starrs/The Washington Post)

The Republican Party is no stranger to extreme candidates. It has lost eminently winnable Senate races by picking unelectable nominees like Todd Akin, Sharron Angle, Richard Mourdock and Christine O'Donnell in recent years. It voted for the leader of the birther movement and a proponent of banning all Muslim immigration as its 2016 presidential nominee — who won.

But even against that backdrop, Roy Moore is in a class all by himself. It's difficult to overstate how unprecedented Moore's nomination is even for today's Republican Party. And it's difficult to overstate how badly all of this could blow up in the GOP's face.

It's not just Moore's extreme positions; it's also the methods he's been willing to employ and the religiosity — both literally and figuratively — that undergirds his entire political being. While the candidates listed above have said controversial things and espoused extreme positions, none were true-believers on par with Moore. This is a candidate who:

The likes of Akin, Angle, Mourdock and O'Donnell all waded into areas that gave GOP leaders heartburn and made unnecessary mistakes as candidates — including bizarre theories about reproduction and rape — but they often apologized or backed off in the name of getting elected. And Trump, for all his extreme policies, is rarely bound by any discernible ideology that can't be altered at a moment's notice.

Roy Moore, a candidate for the U.S. Senate in Alabama, said during a debate on Sept. 21 that "crime, corruption, immorality, abortion, sodomy, sexual perversion sweep our land." (WKRG)

None of them ran as the kind of unapologetic crusader that Moore is. Moore has shown he'll lose his job for the right cause, including disobeying court rulings that run afoul of his view of God's role in America. There will be no controlling or prevailing upon Moore over the next two-and-a-half months before the special election or for the next few years if he joins the Senate; he is a bigger wild card than any of the names mentioned above.

And the fact that he's now the GOP nominee in a lengthy special election could hardly be a worse set of circumstances for Republicans. This is one of just two big races late this year, along with the Virginia governor's race in early November. And you can bet Democrats will try like hell to make it competitive enough to keep Moore in the news until Dec. 12 — even if they don't think they can win.

That will, in turn, force Republicans to explain how this guy fits into their party. Sen. Ron Johnson (R-Wis.) showed how difficult a trick that can be Wednesday morning, telling CNN that “no two people agree 100 percent of the time.” That response works fine for policy differences, but not for arguing that sharia law exists in the United States and that Obama is a Muslim.

Republicans got a healthy dose of “Do You Agree With This” when Trump was running. The whole thing eventually worked out, but it was always an extremely difficult needle to thread — distancing themselves from Trump's most extreme positions while still supporting him.

The Post's Michael Scherer followed Senate candidate Roy Moore (R) in the final days of his primary campaign against Sen. Luther Strange (R-Ala.). Here's a look into his controversial views. (Jenny Starrs,Michael Scherer/The Washington Post)

In Moore, Democrats have almost a caricature of a Deep South Republican whose views would have been outside the mainstream even decades ago. Before Trump, Moore was the kind of candidate Republicans might have disowned or tried harder to beat in the primary. Today, they have to bearhug him and hope against hope that it will all be okay.