U.S. Rep. Denny Heck said Wednesday that he’ll retire from Congress when his fourth term ends next year.

The 67-year-old Democrat from Washington state used the announcement as an opportunity to slam President Trump and other Republicans.

In a letter to supporters, Heck – a member of the House Intelligence Committee -- said the Russia investigation and the Trump impeachment inquiry have left him discouraged and “rendered my soul weary.”

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“I will never understand how some of my colleagues, in many ways good people, could ignore or deny the president’s unrelenting attack on a free press, his vicious character assassination of anyone who disagreed with him, and his demonstrably very distant relationship with the truth,” Heck said.

Heck has represented Washington’s 10th Congressional District, located southwest of Seattle. It encompasses the state capital of Olympia and is considered a Democratic stronghold.

Rep. Dan Newhouse, a Republican from central Washington, said he was proud to have worked with Heck on issues important to the state, including reauthorizing the Export-Import Bank and returning a 9,000-year-old skeleton dubbed “The Ancient One” to local Native American tribes.

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Born in Vancouver, Wash., Heck was a state lawmaker who was first elected to office at age 24. He later served as chief of staff to then-Gov. Booth Gardner from 1989 to 1993.

Heck has declined to endorse some priorities of progressive Democrats, including the Green New Deal and Medicare for all.

He was expected to face at least one Democratic primary in 2020: Joshua Collins, a 26-year-old truck driver and Democratic Socialist who supports the major points on the progressive agenda.

The Associated Press contributed to this story.