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Texas Republicans, with as big a political advantage as any party in the country, are eating their own tail.

In House districts where the Democrats haven’t been putting up a fight, they’re running Republican challengers against Republican incumbents — with Republican Gov. Greg Abbott endorsing some of the challengers.

And a couple of incumbent Republican senators are battling challengers being advised by political consultants affiliated with the Texas Senate’s own presiding officer, Lt. Gov. Dan Patrick.

The Republican Party of Texas added its official institutional punctuation to the GOP’s purist purge last weekend, when the State Republican Executive Committee voted to censure the more moderate Republican House Speaker Joe Straus. Texas has only had two Republican speakers since Reconstruction — Straus and Tom Craddick of Midland — and Straus is one of only three speakers who’ve been elected to the job five times.

But the Texas Legislature is measurably more conservative than it was when Straus was elected. Leaders in the party blame him — or credit him, if you prefer — for flushing the “bathroom bill” and some less-famous measures favored by Patrick, Abbott and others during the 2017 regular and special legislative sessions.

At a time when Republicans hold all of the statewide offices in Texas, overwhelming majorities in the congressional delegation, the Legislature, and a slew of judgeships and local offices across the state, populist conservatives in the GOP are working hard to overthrow the party’s moderates.

It’s a case of self-styled true believers vs. those they’ve labeled as apostates — a political version of the purebloods and mudbloods in Harry Potter’s world. That seemingly ancient idea of pulling everyone together into a “big tent” — remember Ronald Reagan and George H.W. Bush? — appears to be off to the recycling bin.

The Texas GOP certainly has all of the diversity required for a big-tent party, with every possible flavor of conservative. They’re just having a hard time getting everybody to sing from the same hymnal.

The Straus flap should be old news by now. He announced last year that he wouldn’t seek another term as speaker, or even as a state representative. For now, he’s going back to San Antonio. But the party in his home county still voted to censure him in December and pushed the idea up to the state party for consideration.

It almost failed at the executive committee level — the measure needed a two-thirds vote. But “in a sincere effort to foster unity,” the party’s top two officials — Chairman James Dickey and Vice Chair Amy Clark — voted to kick Straus on his way out.

They expressed some misgivings about it, but they voted for censure anyway. “Please know, we do not do this lightly and it does not reflect any personal opinion on particular details in this discussion,” Dickey said in a statement posted on the Republican Party of Texas website. “This is us being committed to supporting the convention, the delegates, Republican voters across Texas in unifying our party to move forward. We must win in 2018. We’ve got to put this this behind us.”

That censure vote is more a reflection of the GOP’s activists and big donors than of its rank-and-file voters. The party chiefs are hollering, but the bigger body of Republicans in Texas — the voters — don’t seem to be worried about it when they vote in congressional and legislative races.

House Republicans, who are elected from 95 of the 150 House districts in the state, have voted time and again to keep Straus in the corner office. His original sin, for some in the party, came in his first election, when fewer than two-dozen Republicans joined with most of the House’s Democrats to overthrow Craddick and put Straus in charge. In each of the four elections since — in 2011, 2013, 2015 and last year — Straus won re-election with the support of almost all of the House’s Republicans. They’re presumably reflecting the will of the voters who put them in office.

Republicans could hardly be more dominant in Texas government than they are today — than they have been, in fact, for the last decade. They’ve passed a remarkable amount of remarkably conservative legislation. And to think they did all of that with a legislative leader that the purists call a RINO — a “Republican in Name Only.”