Looking for something that really matters in the middle of a summer that, as far as campaigns are concerned, contains a lot more smoke than substance? Check out what’s happening in Texas tomorrow.

Both polling and political reporting suggest that previously obscure Tea Party candidate Ted Cruz is extremely likely to knock off Texas’s Lt. Gov. David Dewhurst in a hotly contested runoff election for the Republican Senate nomination there. The winner is almost certain to win; the Democrats have a runoff of their own tomorrow, which will determine whether an underfunded, unknown former state senator can manage to win the nomination over an even more underfunded, even more unknown perennial candidate whose sole strength appears to be that his name sort of sounds similar to someone who was a senator from Texas well before most of the electorate was born. Well, maybe that’s too strong; the tiny electorate in a Senate runoff might just be that old.

Back to Cruz, which is the real story here: Dave Weigel makes two good points, one of which is that Cruz had a fair amount of luck getting here, and the other that he stands to move up quickly in terms of national attention. At least if that’s what he wants and he turns out to be good at it. Neither of those is assured, yet.

The reason this primary matters, however, is that it will be yet another step in the increasing confidence within the Republican Party that there is no such thing as too radical. The truth is that Republicans have, in fact, paid a price for nominating Tea Party favorites; indeed, they might well control the Senate right now if they had nominated more moderate candidates in a few states, and in others they were able to win with radical candidates who still underperformed Republican potential. But in primaries, a reputation for being a Tea Partier certainly appears to be a big plus, and winners are (of course) easier to remember than losers. So if the results turn out to be as expected, it’s going to wind up as another example of how moderates are doomed in the GOP.

And that kind of reputation tends to build on itself. If you’re looking to support Republicans in 2014, you’ll think twice before backing anyone who reminds you of Dewhurst, because you’ll believe you are just wasting your time or money.

The other big point: As far as anyone can tell, there are no actual policy positions in which Cruz is more conservative than Dewhurst. The entire Cruz campaign has been about attitude and unwillingness to ever compromise.

So not only are new Republican members of Congress more likely than ever to be lock-step supporters of whatever currently counts as conservative, but they’re going to be more and more dedicated to fighting, whatever the cost, instead of compromising.

This isn’t likely to end well for anyone.