AUSTIN — Little wonder that Beto O’Rourke seems to be making U.S. Sen. Ted Cruz a bit nervous as the Democrat barnstorms the state, charms a swath of the grass-roots and collects millions of dollars for his longshot effort to topple the Republican incumbent.

Cruz has seen this movie before. He once starred in it.

Six years ago, Cruz was the longshot, an insurgent conservative who started far behind in the polls in the race for U.S. Senate against then-Lt. Gov. David Dewhurst.

Cruz relentlessly traveled Texas, got support from national activists and benefited from a tea party wave sweeping the country, beating the establishment candidate.

Now Cruz is the one to beat as a new surge rolls across the nation — but this wave is composed of Democrats fighting President Donald Trump’s policies and seeking to seize the House and Senate from the GOP.

To be sure, Texas primary election results appear to indicate that Cruz has little need to worry about November, even though Democratic participation soared.

Democrats’ blue wave smacked into the red reality of still-higher Republican turnout.

There were 1.5 million votes cast in the Republican primary for U.S. Senate, and Cruz got 1.3 million of them, or 85 percent, against four unknown foes.

On the Democratic side, O’Rourke got less than half of Cruz’s tally, just 641,337, or about 62 percent of the 1 million-plus votes cast. He had two unknown competitors and the one closest to him, Sema Hernandez, received nearly 24 percent of the vote.

And yet, Cruz isn’t acting like a candidate with nothing to worry about.

The senator and former GOP presidential contender released a radio ad with a smart-aleck jingle attacking O’Rourke, to the tune of the country song, “If You're Gonna Play in Texas (You Gotta Have a Fiddle in the Band).” Cruz’s version: “If you're gonna run in Texas, you can't be a liberal man.”

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By way of “introducing our liberal opponent” to Texas voters, the ad says O’Rourke “wants those open borders and wants to take our guns” and takes issue with him using the nickname Beto.

“I remember reading stories, liberal Robert wanted to fit in. So he changed his name to Beto, and hid it with a grin,” says the jingle.

O’Rourke, a congressman from El Paso, emphasized how long he’s had the nickname by tweeting a photo of himself as a youngster wearing a shirt with the name “Beto” on the front.

As for the jingle’s other jabs, O’Rourke backs immigration reform including “a fair path to citizenship” and gun control measures such as universal background checks and a ban on assault weapons.

On the burning issue of O’Rourke’s nickname, there’s no evidence he wanted to be called Beto in order “to fit in.” But there is plenty of evidence that Cruz began calling himself “Ted” for that very reason.

Cruz, whose given name is Rafael Edward Cruz, devoted part of his memoir to his quest for popularity in junior high school. The diminutive of Rafael is Rafaelito, which in Cruz’s case was shortened to Felito, leading to the torment of his name being rhymed with Fritos, Cheetos, Doritos and Tostitos by other kids.

When he discussed the issue with his mom, Cruz said, she suggested that he could change his name.

“Ted’ immediately felt like me,” he wrote. His father was “furious with the decision,” he said, viewing it as a rejection of him and his heritage. But Ted it stayed.

Asked about this on CNN, Cruz suggested we all lighten up. But there’s a serious undertone to the issue. By emphasizing O’Rourke’s given name, Cruz highlights that the congressman isn’t Hispanic, even though O’Rourke speaks fluent Spanish and is from the border. This could be important, given Hernandez’s performance in the Democratic primary.

At the same time, the primary votes that went to O’Rourke are unlikely to go to Cruz in the general election, since the Republican’s views are anathema to Democratic values. Democrats are working to drive more people to the polls. And despite the hype, Democratic hopes for a November victory are pinned on congressional and legislative races. In statewide races like O’Rourke’s, losing by only single digits would be progress.

Cruz wants no part of Democratic progress, so it makes sense that he’s running hard.

“We have always taken this campaign seriously. We are taking nothing for granted,” Cruz told reporters.

O’Rourke is taking it seriously, too, refusing to play along when CNN anchor Alisyn Camerota asked whether he, as a former punk-rock band member, might come up with a song to counter Cruz’s jingle.

When O’Rourke responded by talking about issues, Camerota asked, “Why aren’t you taking my punk-rock bait?”

“Because I just don't think that's what folks in Texas want us to focus on,” O’Rourke said. “I mean, we can get into name-calling and talk about why the other person's such an awful guy or we can focus on the big things that we want to do for the future of our country, for the generations that will succeed us.

“This is the most critical moment in the most important year of our lifetimes, and we've absolutely got to get it right.”

It’s enough to make someone nervous.