Washington (CNN) Wisconsin Rep. Jim Sensenbrenner, a Republican who is the second-most senior member of the House, announced on Wednesday that he will not seek reelection in 2020.

Sensenbrenner said he will retire in January 2021, at the end of his current term.

He will become the longest-serving Wisconsin congressman in the state's history late next year when he reaches 42 years of service, overcoming former Democratic Rep. David Obey's record of 41 years, nine months and three days.

He is the 13th Republican lawmaker to announce their plans for departure in recent weeks, adding to a growing list of House GOP retirements.

Before running for the House, Sensenbrenner, a Republican stalwart, served in the Wisconsin state legislature for 10 years.

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