Sen. Jon Tester, D-Mont., has won the Democratic primary over his opponent Michael Hummert in the Montana Senate race - a heated contest that could determine which party controls the chamber next cycle.

Tester, a three-term senator, is running for re-election in red state Montana, and his seat has been eyed by Republicans as one of their best pickup opportunities of the 2024 cycle.

Tester has painted himself as a more moderate Democrat, releasing a memo in May of "Tester’s long-standing track record standing up to President Biden," laying out where he apparently disagrees with Biden on a variety of issues.

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Tester is a three-generation Montana farmer, but faces strong 2024 opposition as the only Democrat to hold a statewide position in the state.

Tester faces opposition from former Navy SEAL Tim Sheehy, who is seen by GOP leadership as the best candidate to take on Tester in the general election. 

Sheehy has been endorsed by most of the GOP leadership, including all statewide Republicans in Montana, such as Sen. Steve Daines, Rep. Ryan Zinke and Gov. Greg Gianforte.

The 2024 Senate map sees Democrats defending 23 out of 34 seats up in 2024, making Montana one of the Democrats' most vulnerable seats of the cycle.