Sen. Rob Cowles, the longest-serving incumbent in the Wisconsin Legislature, announced Monday he will retire rather than run in a district now more favorable to Democrats or move under new district boundaries that take effect in November.

Cowles, 73, had originally said he planned to move and run again to represent the bulk of the district he currently serves that is more Republican. He was first elected to the Senate in 1982 after serving four years in the Assembly.

Under the new maps, Cowles was put in the same Green Bay-area Senate district as two other Republican incumbents: Sens. Andre Jacque and Eric Wimberger. That district will now lean slightly Democratic.

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Wimberger has said he plans to move into the same district Cowles had contemplated moving into, meaning they would have faced each other in a Republican primary. Jacque isn't up for re-election until 2026.

Cowles said "after much thought and deliberation," he has decided against seeking re-election.

"I’ve enjoyed the opportunity I’ve had to meet people in the State Capitol and throughout Wisconsin who share my love for the state we call home," Cowles said in his statement. "From the bottom of my heart, I want to thank everyone who wakes up every day working to make our great state an even better place."

He did not address the new maps in his statement.

Cowles has been active on environmental policy, currently serving as chair of the Natural Resources and Energy Committee. He was also the former co-chair of the Senate's Audit Committee, which ordered and reviewed audits of state agencies and programs.

With Cowles' departure, Democratic Sen. Bob Wirch, of Kenosha, will be the longest-serving senator. He was first elected in 1996, after spending four years in the Assembly.

Democratic Sen. Tim Carpenter, of Milwaukee, has more seniority in the Legislature. He was first elected to the Assembly in 1984, but he wasn't elected to the Senate until 2002.