BILLINGS, Mont. — Donald Trump Jr. urged Montana Republicans to rally against US Sen. Jon Tester in the fall election and said Friday that the two-term Democrat had fallen out of step with the state’s voters on issues ranging from immigration to gun control.

Tester came into the crosshairs of President Donald Trump after releasing allegations in the spring that derailed the White House’s Veterans Affairs nominee, Ronny Jackson.

Speaking at the Montana Republican Party’s annual convention in Billings, the president’s son warned that Democrats are highly motivated heading into the November election — but suggested Tester remains vulnerable.

Trump Jr. alleged that Tester was “all for illegal immigration, all for sanctuary cities” and was “writing and proposing legislation against the second amendment.”

“I’m the son of a billionaire from New York City and I have much more of a Montana platform than the senator, the senior senator from this state. That doesn’t make much sense,” Trump Jr. told the crowd of several hundred Republicans.

He was joined onstage by US Sen. Steve Daines, US Rep. Greg Gianforte and Republican senate candidate and State Auditor Matt Rosendale, who is challenging Tester this fall. Rosendale touted his strong support for Trump’s agenda and said Tester was being “corrupted by the swamp” in Washington, DC.

Rosendale prevailed in a four-way primary election on June 5 after outside political groups spent several million dollars promoting his candidacy and attacking his Republican opponents. The heavy spending signaled that wealthy Republican donors have found in Rosendale a candidate they believe capable of toppling Tester, a farmer from Big Sandy who won two previous senate races by relatively narrow margins.

Trump captured Montana by 20 percentage points in 2016.

Tester drew President Trump’s ire in April by releasing allegations that Jackson overprescribed drugs and got drunk on duty.

White House aides said in the aftermath of Jackson’s withdrawal that Trump intends to campaign in Montana. No visit has been formally announced but US Sen. Steve Daines said Friday that he expects it to happen.

Tester has not backed away from the actions he took against Jackson and said in a recent interview that he would welcome a trip by the president to Montana.

“I did my job as a US senator. We vetted him (Jackson) we asked questions, we didn’t get any answers and he pulled out,” Tester said. “I hope (President Trump) comes to Montana. I really do. I hope he comes and looks at some of the veterans clinics we have, here some of the infrastructure needs and some of the border security challenges we have on our Northern border.”