Factbox-Nine US Senate races to watch in 2024

A view of the U.S. Capitol Building in Washington

WASHINGTON (Reuters) -Democrats face a tough fight in the Nov. 5 election preserving their narrow 51-49 majority in the U.S. Senate, as they are defending several incumbents in Republican-leaning states.

Primaries in Ohio and Pennsylvania - two of a handful of states regarded as competitive by nonpartisan election forecasters - have helped to set the field for November. Below are some Senate races to watch:

MARYLAND: REPUBLICAN CHALLENGER

Larry Hogan, the Republican former governor of Maryland and a vocal critic of former President Donald Trump, said on Feb. 9 he would run for an open Senate seat. Though Maryland has not elected a Republican senator since 1970, Hogan was a popular governor and polling suggests the race will be competitive.

David Trone, a congressman and wealthy alcohol retailer, and Angela Alsobrooks, a county executive, are seeking the Democratic nomination for the seat.

Alsobrooks has garnered endorsements from many prominent Democrats, including Governor Wes Moore, Representatives Steny Hoyer and Jamie Raskin and Senator Patty Murray. But Trone has also received prominent endorsements, including from Representatives Adam Schiff and Colin Allred, both Democratic lawmakers who are currently running for Senate.

Maryland's primaries will be held on May 14.

WEST VIRGINIA: EXPECTED SWING TO REPUBLICANS

West Virginia is expected a certain bet to shift into Republican hands, after maverick Democrat Joe Manchin announced he would not run for reelection.

Jim Justice, a wealthy businessman who was a Democrat when he was elected governor in 2016 and the next year became a Republican, is considered to be the frontrunner in the race.

Among his competitors is Alex Mooney, a House lawmaker who represents a district in the northern part of the state and who was first elected to Congress in 2014.

Zach Shrewsbury, a Marine Corps veteran who has worked as a climate justice organizer, is running for the Democratic nomination, as is Glenn Elliott, a small-town mayor.

Don Blankenship, a former coal executive who was imprisoned for conspiring to violate mine safety standards after an explosion at one of his company's mines killed 29 people, has also filed to run for the seat as a Democrat. Blankenship had sought the Republican nomination in 2018.

West Virginia's primaries will be held May 14.

NEW JERSEY: LOOKING TO REPLACE MENENDEZ

Democratic lawmaker Andy Kim is aiming to replace Senator Bob Menendez.

Menendez, who was indicted by federal prosecutors on bribery and obstruction of justice charges, said in a video message in March that he would not seek reelection as a Democrat, but he suggested he could run for reelection as an independent.

Tammy Murphy, the state's governor's wife, had also sought the seat, but dropped her bid last month.

New Jersey's primaries will be held on June 4. Democrats are strongly favored to hold the seat in November.

MONTANA: VULNERABLE DEMOCRATIC INCUMBENT

Democrat Jon Tester is defending his seat in a state that backed Trump during the 2020 election.

Tim Sheehy, a military veteran who founded an aerial firefighting company, is running as a Republican and has drawn the support of other party members in the Senate.

Representative Matt Rosendale, who lost to Tester in 2018, said on Feb. 9 he would also seek the Republican nomination, potentially setting up a divisive primary fight. But Trump endorsed Sheehy that day and Rosendale dropped out of the race less than a week later. Rosendale later said he would not seek reelection to his House seat.

Montana's primaries will be held on June 4.

NEVADA: ROSEN FIGHTS TO STAY ON

Jacky Rosen, a Democrat, is running for a second six-year term in the Senate. The race is expected to be competitive, and 16 people have filed to take her on, nine of whom are Republicans.

Among them are Sam Brown, a military veteran who received a Purple Heart after being injured by a roadside bomb in Afghanistan; Jeff Gunter, a physician and ambassador to Iceland under Trump; and Jim Marchant, a former state lawmaker who has run for several offices in the state.

Nevada's primaries will be held on June 11.

UTAH: CROWDED REPUBLICAN PRIMARY

Utah is an open seat, with Republican Senator Mitt Romney, a prominent Trump critic and onetime party presidential nominee, having said he will not seek reelection. Unlikely to swing to Democratic hands, the state is expected to feature a crowded Republican primary field.

Republicans seeking the seat include the former speaker of the state's House of Representatives, Brad Wilson; U.S. Representative John Curtis; and Brent Hatch, the son of the senator who held the seat for 42 years before Romney.

Utah's primaries will be held on June 25.

ARIZONA: SINEMA DROPS OUT

Democrat-turned-independent Kyrsten Sinema said on March 5 she would not seek reelection in Arizona, reducing the risk of a three-way race and setting the stage for Democratic U.S. Representative Ruben Gallego, a progressive, to face off against a Republican candidate.

The Republicans seeking the nomination include Kari Lake, who had been endorsed by Trump during her unsuccessful 2022 run for governor, and Mark Lamb, a county sheriff.

Though Lake is considered the leading candidate and has amassed endorsements from some Senate Republicans, she has also been embroiled in disputes with other Republicans, including the former head of the state Republican Party.

Arizona's primaries will be held on July 30.

MICHIGAN: CROWDED RACE FOR OPEN SEAT

With Democratic Senator Debbie Stabenow retiring, Michigan's Senate race is poised to be competitive in a state that is also expected to play a key role in the presidential election.

Representative Elissa Slotkin, a former CIA analyst who currently represents a swath of communities west of Detroit, is the clear favorite for the Democratic nomination.

Slotkin's competitors include Hill Harper, an actor who appeared on the popular television show "The Good Doctor," and Nasser Beydoun, a business executive and board member of the Arab American Civil Rights League.

The candidates vying for the Republican nomination include three former lawmakers: Mike Rogers, who headed the House Intelligence Committee; Justin Amash, a founding member of the House Freedom Caucus who broke with his party to call for Trump's impeachment; and Peter Meijer, who was among the 10 House Republicans who voted to impeach Trump over his role in the Jan. 6 attack on the Capitol.

Michigan's primaries will take place on Aug. 6.

WISCONSIN: REPUBLICANS TAKE ON BALDWIN

Democrat Tammy Baldwin is seeking a third term in a state that is expected to be competitive. Eight Republicans and independents have filed to run against her.

The leading candidate for the Republican nomination is Eric Hovde, a wealthy banker who has drawn scrutiny for comments about the voting capabilities of nursing home residents.

Wisconsin will hold its primaries on Aug. 13.

(Reporting by Makini Brice; Editing by Scott Malone, Andy Sullivan and Jonathan Oatis)