Dan Baer can remember being 15 years old in 1992 and watching as Colorado voters passed Amendment 2, which prevented cities and towns from protecting LGBT people. He can remember doubting then whether he would ever have a successful career, especially in public life.

“The idea that I could run for office as a gay person in Colorado, in the ’90s, was far-fetched,” said Baer, now 42 years old, at his home in Denver’s Five Points neighborhood on Monday.

But 2019 looks a lot different than 1992 and Baer is now running for U.S. Senate, joining a crowded Democratic field that hopes to defeat Sen. Cory Gardner, a Yuma Republican, next November. If successful, Baer would be the first openly gay man elected to the Senate.

He is a Harvard and Oxford graduate who was U.S. ambassador to the Organization for Security and Cooperation in Europe between 2013 and 2017 and a deputy assistant secretary of state for four years before that. He served as Colorado’s executive director of higher education last year.

Baer is what his husband calls an enthusiastic institutionalist – “I tell him that doesn’t poll very well, so I better stick with idealist,” Baer joked – who spent four years in Vienna with the OSCE trying to find consensus among 57 countries on issues like human rights and Russian aggression.

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“Cory Gardner sits on the Foreign Relations Committee. I think one of the things I offer as a candidate going up against him is that I can go toe-to-toe with Cory Gardner on foreign policy issues,” Baer said.

He sees a blueprint for success in the 2018 elections of foreign policy-focused Democrats to Congress, including Jason Crow in Colorado’s 6th District. He acknowledges the conventional wisdom that says foreign policy is rarely front and center in voters’ minds but believes that is slowly changing in the era of Trump, when trade disputes are hitting pocketbooks and climate change is affecting commodity prices.

Baer briefly ran for Congress in 2017 when it appeared the 7th Congressional District seat would be open, then dropped out when Rep. Ed Perlmutter changed his mind on retirement.

He joins a growing list of Colorado Democrats who want to take on Gardner. Other announced candidates include former state Sen. Mike Johnston, former House Speaker Andrew Romanoff, scientist Trish Zornio, teacher Stephany Rose Spaulding and community organizer Lorena Garcia.