It largely escaped the notice of the national media, but there has been a pretty big political story playing out in Houston the last few weeks.

Well, it has been a big story, at least, for one very key GOP constituency.

Here's the recap: The city of Houston a few weeks back subpoenaed the sermons of five pastors who opposed an ordinance that was aimed at increasing the rights and protections of LGBT residents of the city, which is home to the first openly lesbian mayor of a major American city, Annise Parker (D). The subpoenas were issued in response to a lawsuit brought by Christian leaders against the new law, which is in limbo because of the litigation. After conservative Christians cried foul, though, Parker announced last week that  the subpoenas were being withdrawn, because they had become a distraction.

And through it all, one of the top potential 2016 presidential candidates has been on the case.

Sen. Ted Cruz (R-Tex.) spoke out against the subpoenas soon after they were issued. He also granted interviews and called for supporters to send Bibles and religious texts to Parker's office, which they did.

And he has now cut a video for the conservative Family Research Council -- a video which amounts to something of a victory lap.

(For further reading, Dave Weigel has a good recap of Cruz's involvement on this issue.)

Of course, Cruz isn't the only potential presidential candidate who got involved. Sen. Rand Paul (R-Ky.) and former senator Rick Santorum (R-Pa.) have also spoken out to lesser degrees, as has former Arkansas governor Mike Huckabee (R), who delivered a strong rebuke to Parker on his Fox News show soon after the subpoenas were issued and was the first to call for people to send her Bibles.

And there's a reason it's these four guys who are getting in on the action; they're all competing for a very key constituency in 2016.

But while Huckabee won the Iowa caucuses thanks to conservative evangelicals in 2008 and Santorum won it for much the same reason in 2012, perhaps no candidate in 2016 has the same kind of inside track on these voters now as Cruz does. After all, nobody is giving Huckabee and Santorum much of a chance to win the nomination at this point, and while Paul has certainly made outreach to these voters a priority, he's got a much broader focus and the fit isn't quite as neat.

Cruz's father, for instance, is a pastor. Also, the younger Cruz speaks very much like a pastor when he's on stage.

Other Republicans, meanwhile, aren't really tapped in to these voters, in large part because they're not a natural constituency. Many of the top GOP hopefuls are Catholic, for one, and few hopefuls want to get involved in a matter involving a fight against a bill to expand gay rights. It's just not what the GOP establishment wants to talk about right now, given its losing hand on issues like gay marriage.

For Cruz, though, that concern with general-election electability is less a concern; he's just not that kind of politician. And these supporters are his bread and butter when it comes to making himself relevant in the 2016 primaries, because they're his ticket to victory in Iowa.

What happens in those churches on Sunday isn't well-understood by the national media, but this was a very big deal for a very key political constituency, and Cruz and others were smart to get involved early on, especially given the religious liberty issues involved.

Expect to hear all of them talk about it a fair amount going forward, as an example of the political left's "war on religious liberty." That's a message that works in some key early primary states.