FACTBOX-Nine US Senate races to watch in 2024

Below are some races to watch ahead of the 2024 election. ARIZONA: SINEMA DROPS OUT Sinema's exit means that Democratic U.S. Representative Ruben Gallego, a progressive, will 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.

U.S. Senator Kyrsten Sinema said on Tuesday she would not seek reelection in Arizona, lifting the threat of a three-way race featuring the Democrat-turned-independent.

Democrats face a tough map in their quest to hold on to or expand their narrow 51-49 majority in the Senate in the Nov. 5 election, since they will need to defend multiple seats in Republican-leaning states. Below are some races to watch ahead of the 2024 election.

ARIZONA: SINEMA DROPS OUT Sinema's exit means that Democratic U.S. Representative Ruben Gallego, a progressive, will 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 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. CALIFORNIA: REPUBLICAN BASEBALL STAR IN THE MIX

Democratic U.S. Representative Adam Schiff, a former House of Representatives Intelligence Committee chairman, will face off with Republican former baseball player Steve Garvey in the race to succeed the late California Democratic Senator Dianne Feinstein. Schiff and Garvey received the most votes in California's primary on Tuesday, in an unusual contest allowing the two top vote-getters, regardless of party, to advance to the general election. Garvey knocked out two U.S. Representatives - Katie Porter and Barbara Lee - to reach the runoff.

Garvey was a popular infielder when he played for the Los Angeles Dodgers and San Diego Padres, but the Senate seat is expected to stay in Democrats' hands in a state that reliably votes for the party. TEXAS: DEMOCRATS EYE OPPORTUNITY

Though Senate Democrats have more seats to defend than Republicans do, they are eyeing some pickup opportunities - namely seats in Texas and Florida. In Texas, where every statewide elected official is a Republican, Democrats are seeking another chance to topple Ted Cruz. Cruz narrowly won reelection in 2018 and faced an outcry when he traveled to Cancun, Mexico, on vacation as the state grappled with a devastating winter storm.

Cruz, who won his primary on Tuesday, will face Democratic primary winner Colin Allred, a former professional football player and civil-rights attorney and a current congressman who represents a district in the Dallas suburbs. OHIO: DEMOCRAT DEFENDING SEAT IN TRUMP-SUPPORTING STATE

Democratic Senator Sherrod Brown is seeking to defend his seat in a state that voted for Trump in the 2020 election. The race to win the Republican nomination so far includes Ohio's Secretary of State Frank LaRose; Matt Dolan, a state senator; and Bernie Moreno, a businessman. Moreno has received Trump's endorsement in the race.

Ohio's primaries will be held on March 19. PENNSYLVANIA: RETURN OF MCCORMICK

Republicans are eyeing the Pennsylvania U.S. Senate seat as a possible opportunity for them in the perennially competitive state. Democrat Bob Casey is running for reelection, where Dave McCormick, a former hedge fund executive, is vying for the seat. McCormick had previously run for Senate in 2022, but lost the Republican primary to television personality Mehmet Oz, who had been endorsed by Trump. Oz went on to lose his race against Democrat John Fetterman.

Pennsylvania's primaries will be held on April 23. MARYLAND: REPUBLICAN CHALLENGER

Larry Hogan, the Republican former governor of Maryland, announced on Feb. 9 that he would run for an open Senate seat. Though Maryland has not elected a Republican senator since 1970, Hogan was a popular governor in the state and polling has suggested the race will be competitive. David Trone, a congressman and wine magnate, and Angela Alsobrooks, a county executive, are seeking the Democratic nomination for the seat.

Maryland's primaries will be held on May 14. MONTANA: VULNERABLE DEMOCRATIC INCUMBENT

Democratic Senator 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 that 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. Montana's primaries will be held on June 4.

NEW JERSEY: LOOKING TO REPLACE MENENDEZ Democratic Senator Bob Menendez so far has not said whether he will seek reelection after being indicted by federal prosecutors on bribery charges. Menendez was hit with a fresh obstruction of justice charge on Tuesday.

Several Democrats are eyeing the seat, including Tammy Murphy, the wife of Governor Phil Murphy, and Representative Andy Kim. New Jersey's primaries will be held on June 4.

UTAH: CROWDED REPUBLICAN PRIMARY Utah is an open seat, with Republican Senator Mitt Romney, a prominent Trump critic and onetime party standard-bearer, having announced he would not seek re-election. Unlikely to swing to Democratic hands, the state is expected to feature a crowded Republican primary.

The candidates seeking the seat include the former speaker of the state's House of Representatives, Brad Wilson; U.S. Representative John Curtis; and Brent Orrin Hatch, the son of the senator who held the seat for 42 years before Romney. Utah's primaries will be held on June 25.