[7] In 1999, Knopp helped enshrine Oregon's unique "kicker" law, which returns excess tax revenue back to taxpayers, into the Constitution by sponsoring referral legislation that brought Measure 86 to the voters in 2000.

[14] On October 22, 2021, Knopp was elected senate minority leader by the House Republican Caucus after Fred Girod stepped down due to personal medical reasons.

[21] Knopp opposed legislation to increase the production of renewable energy and limit greenhouse gas emissions.

[23] In an interview with The Oregonian Knopp said, "I feel no constitutional obligation to stand around so they can pass their leftist progressive agenda ...

[27] Knopp was a leading opponent of legislation in 2015 and 2019 to eliminate non-medical exemptions to the requirement that Oregon schoolchildren be vaccinated.

[30][31] While participating in a Republican-led walkout in May 2023 Knopp reached the 10 unexcused absence threshold set by measure 113, disqualifying him from running for reelection after his current term ends.

[32] Knopp and 4 other Senators filed a lawsuit against Secretary of State LaVonne Griffin-Valade in response, arguing that the measure's wording allowed them to serve one additional term before being barred from reelection.

[34] On February 1, 2024, the Court unanimously ruled against the Republican Senators, confirming Knopp's disqualification after the end of his term in January 2025.

"[36] Knopp's term ended on January 13, 2025, and he was replaced by Anthony Broadman, the first Democrat to represent the district in over 40 years.

[37] Following the Standoff at Eagle Pass, Knopp signed a letter in support of Texas Governor Greg Abbott's decision in the conflict.