State Senate Minority Leader David Schapira is running for the U.S. House seat from Arizona's 9th Congressional District.
Schapira made the announcement during a news conference Tuesday.
The Tempe Democrat was elected to the state Senate in 2010 after serving in the House for four years. Schapira is also a university faculty member and a former high school teacher.
Democrat Kyrsten Sinema of Phoenix resigned from the Arizona Senate earlier this month to run for the same seat.
Schapira has said he will not resign from his Senate seat. He is in the last year of his term and is not required to step down under the state's resign-to run-law.
Republican Travis Grantham, an Arizona Air National Guard Captain and business owner announced last week he was also running for the seat.
Republican U.S. Rep. Ben Quayle also lives in the district, but he may run instead in an adjacent district.
The newly drawn 9th District includes much of central Maricopa County, taking in Tempe and parts of Phoenix and Mesa.
A state redistricting commission voted to approve new congressional districts for the state on Tuesday.