Donald Trump Jr. will campaign for rancher and state auditor Matt Rosendale in Montana to help defeat Sen. Jon Tester (D-MT), according to a Rosendale press release on Tuesday.

Donald Trump Jr. will join Rosendale at the Montana Republican party platform’s convention in Billings, Montana, on June 22, where Don Jr. will be keynote speaker.

Rosendale said in a press release on Tuesday:

Make no mistake, the people of Montana will elect someone with a flat-top as their next U.S. Senator this November. The question is: Will he support President Trump’s agenda or not? I’m honored to have Trump Jr.’s support because he knows I’ll back his father’s agenda and will work with him to Make America Great Again. Montanans have had enough of Jon Tester’s political games, smear tactics, and liberal obstruction.

Rosendale, Sen. Steve Daines (R-MT), and Rep. Greg Gianforte (R-MT) will also speak at the Montana GOP convention.

Rosendale recently won the state’s Senate Republican primary, which will place him against Sen. Tester in the general election.

The Montana Republican released a new campaign ad on Tuesday that focused on helping President Donald Trump build his promised wall on the southern border with Mexico.

Rosendale said in the ad, “Jon Tester had a chance to stop sanctuary cities, but he voted with them. “I’ll stand with President Trump. We’ll get tough, and we’ll build that wall.”

In another press release on Tuesday, Rosendale attacked his Democratic opponent for working with coastal elites to protect illegal immigrants.

Rosendale charged, “While Jon Tester and the liberal coastal elites fight President Trump to protect illegal immigrants. Matt Rosendale is committed to standing with President Trump to crack down on illegal immigration and see to it that we finally build the wall.”

Tester voted three times to fund sanctuary cities, voted to shut down the government over amnesty for illegal immigrants, and voted against funding President Trump’s border wall.

Rosendale’s conservative accolades as a state auditor earned him the endorsements of over 30 Montana state officials as well as Sens. Rand Paul (R-KY), Ted Cruz (R-TX), and Mike (R-UT).

National Republican Senatorial Committee (NRSC) spokesman Calvin praised Rosendale in a statement on Tuesday, saying:

Unlike Senator Tester, Matt Rosendale will stand with President Trump to crack down on illegal immigration and fix our broken borders. Montanans deserve a Senator who will stand up and fight, not another rubber stamp for Washington liberals like Senator Jon Tester.

Rosendale told Breitbart News in an exclusive interview that “Jon Tester is not a moderate Democrat, he is part of the swamp.”