Arizona Representative Ruben Gallego has announced his bid for Kyrsten Sinema’s Senate seat, challenging the incumbent Democrat.

Gallego, a former Marine Corps reservist and Iraq War veteran, has represented Arizona’s 7th congressional district since 2015. He has made a name for himself in Congress as an advocate for the military and veterans, and for progressive causes.

In a statement, Gallego said, “We must continue to fight for progress and progressivism in the Senate. I am running to make sure that we continue to build on the progress that Kyrsten Sinema has made in the Senate, and to continue to fight for our progressive values.”

Sinema, who was elected to the Senate in 2018, has yet to comment on Gallego’s announcement. However, according to The Arizona Republic, Sinema will have the ultimate say in who replaces her in the Senate.

Gallego’s Senate campaign is sure to be closely watched in the coming months.