Rep. Ruben Gallego (D-AZ) is set to launch a bid for the United States Senate, reportedly as soon as Monday, that would potentially challenge Sen. Kyrsten Sinema (I-AZ).

The former Marine combat veteran, who’s been “encouraged” to run for Senate against Sinema by Democrat senators, is getting ready to announce his run for Senate, first reported by Newsweek.

Gallego has been vocal about his frustration with Sinema, which grew stronger after she left the Democrat Party. The Democrat, as reported, intends to make his announcement via video in English and Spanish, according to three sources the campaign had briefed.

For weeks, he’s been interviewing and hiring the necessary people to make a run against the incumbent Independent senator, who left the Democrat Party last year after the midterms. He also is the chair of BOLD PAC, the political arm of the Congressional Hispanic Caucus. which will more than likely help him raise large sums of money.

However, Sinema has yet to make an official announcement on whether she will run for reelection or not. She has filed campaign papers with the Federal Election Commission (FEC) for the 2024 election cycle, noting her recent party change to allow her committee to continue fundraising while she makes a decision.

If Sinema runs in the Democrat primary, she could potentially run as a third-party candidate after the primary if she loses. But, running as a third-party candidate would also have the potential to split the votes and help elect a Republican. Last month, Politico explained one option that would allow the Arizona senator’s party switch not to cause a contested Democrat primary but could end up making a “nightmare scenario” for the party:

With three candidates on the ballot, a GOP nominee can capitalize on centrist and liberal divisions and win a Senate seat with a plurality vote. Democrats are not eager to intervene at the moment, but at some point they may have to make a call about whether to support Sinema, back whoever wins a primary or sit out the race altogether.

So, with only a slim 51-seat majority, the Democrat Senatorial Campaign Committee (DSCC), the Senate Democrats’ campaign arm, will not only have to try to keep the 51-seat majority but will also potentially have to spend millions of dollars protecting Sinema, a valuable incumbent for the left, in addition to some Democrat senators running in states that have turned redder over the years.

Jacob Bliss is a reporter for Breitbart News. Write to him at jbliss@breitbart.com or follow him on Twitter @JacobMBliss.