Donald Trump Jr. took a jab at Texas Senate candidate Beto O'Rourke on Twitter Monday for "pretending to be Hispanic."
"What’s authentic about an Irish guy pretending to be Hispanic? Asking for some friends Texas," Trump Jr. tweeted.
Along with his tweet was the link to an ABC News story that described O'Rourke as a candidate that Democrats considered to be "authentic."
O'Rourke, whose real first name is Robert, is challenging Republican Sen. Ted Cruz for his seat.
The Democrat from El Paso, Texas, has claimed that Beto is the nickname he's been called since he was a child in school.
El Paso is a primarily Hispanic city that sits on the Texas-Mexico border.
What did Cruz say about O'Rourke's nickname?
Trump Jr. isn't the only one to have questioned O'Rourke's motives for using a Latino sounding nickname.
In a radio ad released by the Cruz campaign earlier this year, Cruz called out O'Rourke for changing his name.
"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," the ad says. "So he changed his name to Beto and hid it with a grin."
What about Cruz's first name?
The senator's full name is Rafael Edward Cruz but he goes by Ted, a common nickname for his middle name Edward.
"You're absolutely right. My name is Rafael Edward Cruz," he told CNN when asked about his nickname. "I am the son of my father Rafael Cruz, an immigrant from Cuba who came to Texas with nothing."
In other attempts to portray himself as an average Texan, O'Rourke has jumped on stage with pot-smoking country music star Willie Nelson, hit the Whataburger drive-thru after town hall meetings and even skateboarded to a recent rally.
From July to September, he hauled in a record-setting $38.1 million from individual contributions for the most money collected in a single quarter by any U.S. Senate candidate.
During the same period, Cruz raised $12 million and he has gained momentum in the polls.
Cruz has an average lead of 7 points over O'Rourke in the most recent polls.