By Moira Warburton
(Reuters) -U.S. Senator Jon Tester of Montana launched his 2024 reelection bid on Wednesday, in a plus for Democrats, who are seeking to defend their slim 51-49 Senate majority but will face challenges in several battleground states next year.
Tester, 66, who has represented Montana in the U.S. Senate since 2007, is a reliable moderate Democrat who has won three tight races in the past in an increasingly Republican state.
"Montanans need a fighter that will hold our government accountable and demand Washington stand up for veterans and lower costs for families," Tester said in a Twitter post declaring his reelection campaign. "I will always fight to defend our Montana values. Let's get to work."
Two Republicans now serving in the U.S. House of Representatives -- Matt Rosendale and Ryan Zinke -- are seen as potential candidates in Montana's 2024 U.S. Senate Republican primary. State Attorney General Austin Knudsen is also viewed as a possible contender.
Tester - a former music teacher with a reputation for folksy, down-to-earth authenticity - defeated Rosendale by less than 4 percentage points in 2018.
He will likely face a tough battle for reelection, even with an incumbent's advantage, in a Western state where Republicans have swept statewide races by wide margins in recent years.
In 2020, Republican U.S. Senator Steve Daines bested former Democratic Governor Steve Bullock by more than 10 percentage points. That same year, Republican President Donald Trump defeated Democrat Joe Biden in Montana, winning the state by more than 16 points while losing the national election.
Montana is one of several states, including West Virginia, Ohio and Arizona, that present challenges to the Democrats' ability to hold on to their Senate majority going into 2025.
Arizona U.S. Senator Kyrsten Sinema in December left the Democratic Party, changing her registration to independent. While she continues to caucus with President Joe Biden's party, along with two other independents, her move could lead to a three-way race in the Southwestern state in 2024 between the incumbent, a Democratic candidate and a Republican challenger.
Democratic U.S. Representative Ruben Gallego last month said he would seek his party's nomination to challenge Sinema.