Sen. Ted Cruz’s reelection campaign would really like Texas voters to know that Rep. Beto O’Rourke, the Democratic challenger hoping to turn Texas blue in November, is using a nickname, and that his birth name is Robert Francis O’Rourke.

In a statewide radio ad released almost as soon as the primary races were called, Cruz’s campaign took a shot at the legitimacy of O’Rourke’s identity. The El Paso, Texas, Democrat, who is mounting a more serious but still extremely long-shot challenge to the incumbent Republican senator, won the Democratic Texas primary Tuesday night with 61.8 percent of the vote. He still faces a very tough road ahead in a state that is trending purple but doesn’t look like it’s quite there yet.

Cruz’s ad, a country jingle, said: “If you are going to run in Texas, you can’t be a liberal man. I remember reading stories, liberal Robert wanted to fit in. So he changed his name to Beto and hid it with a grin.”

Cruz defended the ad on CNN Wednesday morning, saying “some of it is just to have a sense of humor. ... We had some fun with it.”

The origin of O’Rourke’s Hispanic-sounding first name has been captured in almost every profile of the rising Democrat: “Beto” is a childhood nickname that stuck. And ironically, when it comes to first names, O’Rourke and Cruz have something in common: Cruz goes by “Ted,” but he was born Rafael Edward Cruz. Cruz didn’t shy away from that when asked to defend the ad, instead launching into a story about his Cuban immigrant father.

Birth names aside, Cruz’s jab at O’Rourke gets at a much more serious question of authenticity. In a deeply red state with quickly changing demographics, Cruz and O’Rourke represent two very different versions of Texas. And it appears Cruz is taking O’Rourke’s Texas seriously.

Cruz’s campaign is trying to drum up controversy around the name “Beto”

Attacks on the legitimacy of O’Rourke’s first name aren’t new.

When O’Rourke announced his Senate campaign bid last year, the right-wing Free Beacon ran an article headlined “Meet the Irish-American Going by a Mexican Nickname Challenging Ted Cruz.” The article argued that O’Rourke’s “Mexican nickname” helped him in a primary challenge against an actually Hispanic incumbent Democrat:

O’Rourke, 44 years old, is the son of Patrick Francis “Pat” O’Rourke, an El Paso judge whose family immigrated to the United States from Ireland three generations earlier. It was in El Paso that the young Robert began going by “Beto,” a common nickname in Mexico for people named Roberto. The Mexican nickname came in handy in 2012 when O’Rourke decided to challenge eight-term incumbent Democrat Silvestre Reyes in a congressional district that is 75 percent Mexican and just 2 percent Irish.

Now Cruz’s allies have picked up on the same thread. Jeff Roe, a Republican strategist who served as Cruz’s campaign manager during the 2016 presidential election, tweeted a side-by-side photo of O’Rourke signing “Robert” on a legal court document but “Beto” on a congressional letter.

Roe went on to say that O’Rourke penned college papers as Robert and rowed crew under his birth name as well — seemingly trying to poke holes in O’Rourke’s explanation of his name as simply a childhood nickname.

“My parents have called me Beto from day one, and it’s just — it’s kind of a nickname for Robert in El Paso. It just stuck,” O’Rourke told CNN, adding that he has a baby picture of himself in a hand-knitted “Beto” sweater. “I just don’t think that’s what folks in Texas want us to focus on. ... We can focus on the small, mean, petty stuff or we can be big, bold, courageous, and confident.”

O’Rourke’s campaign said they had no further comment on the issue, but the Democratic lawmaker did post a childhood photo wearing a sweater with “Beto” hand-stitched on the front.

In college, Cruz went by “Rafael E. Cruz,” “Rafael Ted Cruz” and “R. Ted Cruz” depending on publication, as the Boston Globe’s Matt Viser pointed out. He was “Rafael E. Cruz,” at the Harvard Latino Law Review, “R. Ted Cruz” at the Harvard Journal of Law and Public Policy, and “Rafael ‘Ted’ Cruz” in the yearbook.

As long as we are talking about names...Ted Cruz was listed as “Rafael E. Cruz” at the Harvard Latino Law Review, as “R. Ted Cruz” at Harvard Journal of Law and Public Policy, and “Rafael ‘Ted’ Cruz” in the yearbook. pic.twitter.com/NXDJHkUDo2 — Matt Viser (@mviser) March 8, 2018

Behind all this back-and-forth is a debate about identity. On the right, the case is that O’Rourke is abandoning his white identity, associating instead with the Hispanic immigrant culture from his hometown, while Cruz has done the opposite.

Ted Cruz seems to be taking this challenge seriously

O’Rourke has been getting a lot of national attention as the candidate breathing life back into the long-held Democratic dream of a blue — or at least purple — Texas.

It’s still an incredibly long-shot bid. O’Rourke didn’t come close to garnering the same number of votes as Cruz did in the primary, and even he admits the math doesn’t really “add up” for him.

But there has been an undeniable wave of Democratic enthusiasm across the nation that’s given O’Rourke, and other long-shot Democrats, hope of being competitive. O’Rourke, who isn’t taking Super PAC money, has repeatedly out-fundraised Cruz, reportedly raising almost three times as much as Cruz in the first 45 days of 2018.

The climate has spooked Republicans.

“I think one thing that is underappreciated is that, by and large, the climate in Texas is not that different [from] the climate in the country,” Jim Henson, who directs University of Texas’s Texas Politics Project, said. “Partisans are seriously divided on the issue of Donald Trump. Democrats are by and large critical; Republicans are by and large sticking by him.”

It’s clear Cruz has been watching.

At a GOP event before the Texas primary, Cruz told supporters that Democrats would “crawl over broken glass in November to vote,” warning that Republicans “could get obliterated at the polls.”

He’s making the case that O’Rourke is a gun-grabbing, tax-raising, left-wing liberal who has no place in Texas. But until now, Cruz has largely been keeping out of the political spotlight in the US Senate.

“He’s been less flamboyant,” Austin-based conservative strategist Matt Mackowiak said. “[Cruz is] playing the inside game now. He has been effective on legislation, fought really hard on the disaster relief effort. He’s just not making news on the national level, and that was always a dilemma for what someone like him does when you are in the majority.”

Meanwhile, Democrats’ hopes hinge on the state’s growing, and young, Hispanic population. Maybe too young for 2018. As the Texas Tribune’s Alexa Ura and Ryan Murphy point out, “a third of Texas Hispanics aren’t even of voting age. In fact, those under 18 make up the state’s largest Hispanic age group. Meanwhile, those aged 45 to 64 make up the biggest age group of white Texans.”

Even so, the demographics of O’Rourke’s base put the attacks against “Beto” at a particularly interesting nexus — and are a clear sign that Cruz’s campaign recognizes O’Rourke as a more serious candidate.