By BOBBY CAINA CALVAN, Associated Press

HELENA, Mont. (AP) — Montana state Auditor Matt Rosendale said Monday he will seek the Republican nomination to run against incumbent U.S. Sen. Jon Tester, considered one of the most vulnerable Democrats seeking re-election in 2018.

Rosendale joins a growing list of Republicans who have announced their candidacy or their interest in the Senate post. National Republicans have hoped to draw a higher-profile candidate to run against the two-term Democrat.

"I've been getting calls from across the state from people who are just not satisfied with the job Tester's doing," Rosendale said. "They feel like he comes here back home and he acts like a good old farmer and yet he goes back to Washington, D.C., and he votes with and just like Chuck Schumer," the Democratic minority leader from New York.

Billings Judge Russell Fagg, a former state legislator who is considering his own Senate run, took a jab at Rosendale's residency in Montana. Fagg said his "four generations of Montana roots, all the way back to the late 1800s" puts him in a better position to understand the problems faced by Montanans.

Rosendale moved to the state 16 years ago from Maryland and noted that voters have repeatedly elected him to public office.

In November, Rosendale won a four-year term as auditor to oversee the insurance and securities industries in Montana. He previously served in the Legislature, representing the Glendive area.

He ran unsuccessfully for the U.S. House in 2014, losing in the primary to fellow Republican Ryan Zinke, who is now Interior secretary.

Democrats have been anticipating a bid from Rosendale and have in recent months assailed him for seeking a repeal of the Affordable Care Act.

Rosendale also said he will campaign on strengthening programs for military veterans and increasing resources for the Defense Department.

Lots of outside money is expected to pour into Montana for the race, as has been the case with other closely watched contests and because of Tester's stature among congressional Democrats. As of June 30, Tester had $4.7 million in campaign money.

"Jon Tester is as Montanan as it gets and it shows every day he's working in the U.S. Senate," his campaign manager Christie Roberts said in an email. "He is proud of his record of fighting for Montana, and he's ready to stack that record up against anyone."

Democrats are hoping to retake the U.S. Senate next year but must defend 23 of the 33 seats up for election.

National Republicans had courted Montana Attorney General Tim Fox to make a bid after Zinke decided to join President Donald Trump's administration. Fox declined, leaving the field wide open.

Among the other Republicans seeking their party's nomination are state Sen. Albert Olszewski and Big Sky businessman Troy Downing.