Arizona state Rep. Ruben GallegoRuben GallegoOvernight Defense: North, South Korea to march together at Olympics | Lawmakers react | Trump says Russia helping N. Korea skirt sanctions | Tillerson lays out Syria strategy with indefinite US military commitment Dems after Asia trip: No 'illusions' about N. Korea's nuclear work amid Olympics talks WATCH: Dem lawmaker: House immigration bill can't 'make it through the Senate' MORE (D) got the backing of Rep. Raúl Grijalva (D-Ariz.) in his bid to replace retiring Rep. Ed Pastor (D-Ariz.).

Grijalva said in a statement that he “couldn’t think of a better candidate” to replace Pastor than Gallego.

"Ruben possesses a lot of the qualities that made Ed one of the most effective legislators I ever worked with," Grijalva said. "Ruben is a fierce advocate for what’s right, as he has already shown with his leadership on climate change and income inequality. He’ll be a force for Arizona in Congress and I can’t wait to work with him."

Gallego is one of at least four Democrats vying for the seat in a crowded primary that’s expected to grow. Arizona’s 7th District is a safe Democratic seat, so whoever takes the nomination is expected to easily win the general election.

Though the field is still developing, Gallego launched his campaign almost immediately after Pastor announced his retirement plans and was soon after endorsed by, a pro-veterans group, as well as former Arizona Democratic Rep. Harry Mitchell.