Former state Sen. Mike Johnston picked up an interesting, though not surprising, endorsement Tuesday in his run for the U.S. Senate.

State Rep. Tom Sullivan of Centennial threw his support to Johnston in the crowded Democratic primary. Sullivan, like Johnston, is an advocate for more restrictions on guns.

Sullivan’s son Alex was one of 12 people killed in the 2012 Aurora theater mass shooting.

Johnston’s political career is party defined by his work on 2013 legislation to ban high-capacity magazines and require universal background checks on gun sales.

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“Mike Johnston showed that you can take on groups like the gun lobby and the NRA and you can be successful,” Sullivan said in a statement Tuesday. “Mike Johnston is what we need in Washington, D.C., to fight for and be a voice for my son Alex.”

Sullivan’s profile among Democrats was lifted higher as Republicans initially sought to recall him, only to give up. Left-leaning groups were prepared to spend big to defend the seat and send a message they wouldn’t be intimidated by gun-rights activists.  

Sullivan’s endorsement is featured in a series of videos called “The Mike Johnston I Know.” The three videos so far — also featuring Samantha Garcia, former student of Johnston’s at Mapleton Expeditionary School of the Arts, and Park Hill community leader Gerie Grimes — can be seen on Johnston’s campaign website by clicking here.