Ken Toltz, the Boulder Democrat and longtime gun-control advocate, announced Sunday he is suspending his campaign to replace U.S. Rep. Jared Polis because of a serious health situation in his immediate family, narrowing the field for what was in all likelihood his top rival in the race, Joe Neguse.

“It’s a very difficult decision, which is the right one,” Toltz said in a written statement. “My time and attention has been focused on a serious health situation in my immediate family. Mounting a competitive campaign to represent Colorado’s 2nd Congressional District is full-time in itself, and now is not the time for me.”

He added: “I remain engaged and focused on compelling Washington to uphold its primary responsibility, protecting the public safety and to accept their obligation of implementing a comprehensive gun violence solution.”

Toltz’s exit from the race creates a clearer path to victory for Neguse, a fellow Democrat and former Cabinet member of Gov. John Hickenlooper who had won endorsements from many of the party’s top names in Colorado.

Toltz announced his candidacy in early October. He ran unsuccessfully in 2000 in the 6th Congressional District against Republican firebrand Tom Tancredo, a contest that happened in the wake of the Columbine High School shootings.

Tancredo is now running as a Republican for governor.

In 2013, Toltz created Safe Campus Colorado as a way to push back against efforts to allow the concealed carrying of firearms on the state’s college campuses.

Other Democrats running for Polis’ job in 2018 include Nederland Mayor Kristopher Larsen and Mark Williams, former chairman of the Boulder County Democratic Party.

Nick Thomas has filed to run for the position as an independent. Peter Yu has filed to run as a Republican.

Polis is leaving his seat as he runs for governor.

Polis’ strongly left-leaning seat is made up of all of Boulder and Larimer counties and spans into Broomfield, Clear Creek, Eagle, Gilpin, Grand, Jefferson, Park and Summit counties.