The Senate race between David Dewhurst and Ted Cruz is shaping up to be the most important race in many years, going back to the Bush-Richards governor’s race of 1994. That race settled that Texas had become a Republican state and would remain one going into the future. The Dewhurst-Cruz race is likewise a watershed race. It will determine whether the Texas Republican party ventures into the roiling waters of ideological purification, as has happened in states like Arizona and Kansas and South Carolina or whether it can right the ship and return to a relatively normal course of governing.

Ted Cruz is the key figure. He has galvanized a constituency of extremists who threaten a tea party takeover of Texas politics. Rick Perry is to blame for this; it was he who jump-started the tea party movement in Texas in April of 2009. He gave it legitimacy at a rally by saying, “They say you’re a bunch of right-wing extremists, and if you are, I’m for you.” (The quote is not exact, but you get the idea.) And, of course, he hinted broadly that he supported secession. Too late, Perry must face up to the fact that he bears much of the responsibility for the extremism of the Republican party; he cannot control the forces that he unleashed, and he has reaped the whirlwind. The tea party is a mortal threat to the mainstream Republican party.

I wonder what went through Perry’s mind when he was booed at the Republican convention for supporting Dewhurst for Senate. He thought he could manage the flow of events but he couldn’t. Cruz had done what no one else in Texas politics had done, except possibly Debra Medina in 2010: He had gotten to Perry’s right. Perry’s  endorsement of the Dew was worthless, just counterfeit coin.

This is what happens when a party loses interest in governing, when all that its once and future leaders care about are issues that do not improve the lot of its citizens: Voter I.D., sanctuary cities, mandatory sonograms, purging the voter rolls, and fighting the federal government at every turn. How can Republicans endure as a mainstream party when an insurgent candidate for U.S. Senate invokes the word “moderate” to condemn his opponent?

It is unfortunate that Dewhurst is cast in the role of defender of the faith. The poor guy has nothing to offer except snuggling up to Rick Perry. He has been in office for ten years and has little to show for it except a decade of toadying to the governor. I can’t think of a single achievement Dewhurst can claim while in office that isn’t also a Perry achievement. Well, the property tax cut of 05-06 was driven by the lieutenant governor’s office. The problem with Dewhurst isn’t that he doesn’t get what is going on. He gets it. It’s that he doesn’t have the political will to do something about it. Hence, the about-face on using the Rainy Day Fund last session, after which angry senators told me on the Senate floor that if there had been a vote of confidence on Dewhurst, the tally would have been 31-0 against.

Make no mistake: the future of the Republican party is on the line in the Senate race. This is a “For Whom the Bell Tolls” moment. If Cruz wins, it means that powerful Washington interests with the ability to spend far more than our home-state politicians and sugar daddys, are poised to insert themselves into Texas politics and change its course. Even Perry understands this, which is why he is all-in for Dewhurst. What is going to stop the tea party and its deep-pockets national backers from taking over Texas politics with money that comes from outside the state? What is to stop them from uniting behind another Ted Cruz-like candidate to defeat Rick Perry’s bid for reelection. This is exactly what has happened in the Senate race, and it will continue to happen in future race.

There is another aspect to the Dewhurst-Cruz battle, and it is the tendency of the mainstream Republicans to fail to act in their own best interests. It is stunning to me that Greg Abbott continues to harass Hispanics with Voter I.D. and purging the voter rolls: that he can’t see the damage it is doing to the party’s future. He is willing to trade long-term political gain for his party in return for short-term political gain for himself.

The tea party is an immediate threat but not a long-term one; it is a one-generation phenomenon, the last gasp of old angry uninformed white guys. Hispanics are a different story; they represent the future and without them the Republicans have no future. Does it change anyone’s thinking? Apparently not.

I had a conversation with a nationally known Republican consultant yesterday . Here is what he told me: “If Ted Cruz wins the Senate race, Texas will be a purple state in four years.” In other words, the tea party is so extreme that even a Democrat might be able to get elected. Does it change anyone’s thinking? Probably not.