Democrat and gun control activist Ken Toltz on Monday announced he’s suspending his campaign for the congressional seat held by U.S. Rep. Jared Polis, who is running for governor.

Toltz said in a release he’s putting the campaign he launched in early October on hold to focus his attention on what he called a serious health situation in his immediate family.

The departure leaves three Democrats running in the Democratic-leaning seat: former CU Regent Joe Neguse, Nederland Mayor Kristopher Larsen and former Boulder Democratic Party Chairman Mark Williams. Neguse, who has won the lion’s share of endorsements from top Democrats, stepped down this summer as executive director of Colorado’s Department of Regulatory Agencies and lost a race for secretary of state in 2014.

“It’s a very difficult decision which is the right one,” Toltz said in a 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.

“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 lost a bid in 2000 challenging then-incumbent U.S. Rep. Tom Tancredo in the 6th Congressional District in the wake of the Columbine High School shootings, which took place within the district. Toltz focused that campaign on preventing gun violence and later founded the Safe Campus Colorado organization.

Republican Peter Yu, Libertarian Todd Mitchem and independent candidate Nicholas Thomas have filed to run for the seat, which includes Boulder, Larimer and Broomfield counties and mountain counties surrounding Interstate 70 west to Vail. A Republican hasn’t been elected to represent the district since 1972.