Matt Rosendale, fresh off his GOP U.S. Senate primary victory in Montana, launched his general election campaign in earnest Tuesday with a strong push on immigration.

The Rosendale campaign released a television ad attacking incumbent Sen. Jon Tester (D-MT) on his immigration record and positioning Rosendale in President Donald Trump’s camp on the issue in a state Trump won by 20 points in 2016:

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

An accompanying Rosendale campaign press release cites Tester’s immigration record, including his opposition to defunding so-called “sanctuary cities” and his vote against “Kate’s Law.” The latter bill, named after Kate Steinle, who was killed by a bullet a five-time deported illegal alien multiple felon fired, would have imposed mandatory minimums on felons who illegally re-enter the U.S.

“While Jon Tester and the liberal coastal elites fight President Trump to protect illegal immigrants,” the release states, “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.”

Rosendale, the sitting Montana state auditor, secured the Republican nomination to challenge Tester in last week’s primary, triumphing over former Montana judge Russell Fagg.

Jon Tester, whom Rosendale hopes to unseat is a quintessential red state Democrat and a top target for Republicans in 2018. Rosendale and others on the right have sought to portray him as a “swamp”-aligned politician out of step with Montana’s overwhelmingly conservative electorate.

Rosendale has, since the start of his campaign, run as a conservative populist in the Trump vein. In his primary campaign, he received the endorsement of sitting conservatives Sens. Rand Paul (R-KY), Mike Lee (R-UT), and Ted Cruz (R-TX).

Early polling puts a “generic Republican” well ahead of Tester in March, further highlighting the Montana race’s status as a Republican target for November. In April, the race also attracted the personal interest of the president after Tester’s office promoted a two-page dossier collecting accusations against White House physician Dr. Ronny Jackson, who was a potential Veterans Affairs nominee.