"I'm running for Congress because we need a leader who will fight to create new jobs, stand up for middle-class families and protect our seniors," Aguilar said in his announcement. "Congressional Republicans have the wrong priorities and are more focused on partisan bickering than on getting things done. It's time to stop playing political games and start working for the people of the Inland Empire."

Aguilar ran for the seat now held by Miller last year and appeared to have the inside track to win the Democratic-leaning seat. But because of quirks in California's election system and a Democratic spoiler candidate, he failed to make it out of the all-party primary. Miller defeated another Republican in the general election.

The seat appears to be one of the Democrats' best pickup opportunities this election — President Obama won it by 17 percentage points in 2012 — and Aguilar is well-known in the district and, as a centrist Hispanic, gives Democrats a potentially strong candidate for the seat.