New York Rep. John Katko, one of just nine House Republicans to represent a constituency that also voted for Joe Biden, announced Friday that he would not seek a fifth term in the Syracuse-based 24th Congressional District. Katko last year was also one of the 10 GOP members who voted to impeach Donald Trump, which almost certainly would have ensured him serious opposition in the June primary; two other members of this group, Ohio’s Anthony Gonzalez and Illinois’ Adam Kinzinger are also not running for re-election.

It remains to be seen just what will happen to Katko’s constituency. The current version of the 24th backed Biden 53-44 four years, but as Katko’s resilience demonstrates, this area remains quite friendly to Republicans down-ballot. However, no one knows what this district will look like after redistricting, especially since legislative Democrats have the numbers needed to pass their own map.

The Democratic primary already consisted of 2020 candidate Francis Conole, Steven Holden, and Air Force veteran Sarah Klee Hood; more will likely take a look now. On the GOP side, Katko’s leading intra-party foe looked like physician assistant Tim Ko, though the race was still coming together when the congressman called it quits.

Katko’s departure ends an eventful electoral career that began less than a decade ago when he left his job as a federal prosecutor to challenge Democratic Rep. Dan Maffei in the 2014 cycle. Maffei had been narrowly unseated during the 2010 red wave by Ann Marie Buerkle before winning their rematch two years later, but it initially looked like it would be very difficult for Katko to deal him another midterm loss.

Maffei had beaten Buerkle 49-43 as Barack Obama was carrying the seat by a wide 57-41, and while the congressman had been caught by surprise in 2010, he gave every indication that he wouldn’t get caught off guard this time. Katko himself also only wound up with the GOP nod after considerably more prominent names declined to run. Polls additionally indicated that Maffei was in good shape for most of the race, with Siena College giving him a 50-42 lead over Katko weeks after Labor Day.

However, the Republican, who ran a strong campaign focused on his own prosecutorial background, also used Maffei’s new $700,000 home in the D.C. area to argue that the congressman had left the Syracuse area behind. This race ended up attracting millions from both parties as it became increasingly clear that Maffei was once again vulnerable in what was shaping up to be a good year for Republicans.

Plenty of observers were still extremely skeptical about the accuracy of a late October Siena poll giving Katko a 52-42 lead, especially after Maffei released an internal finding him still ahead, but that Siena survey turned out to be off in a way almost no one expected. Katko pulled off a 59-40 win days later, which gave him one of the broadest general election victories over a scandal-free incumbent we’ve ever seen.

National Democrats hoped that the seat would snap back in 2016 with a presumably more favorable climate, making Katko a top target. Team Blue’s nominee this time was Colleen Deacon, a former district director for Sen. Kirsten Gillibrand, and both parties once again spent heavily. Democrats also hoped that Trump’s toxicity would drag down the new congressman, but that very much did not happen: Hillary Clinton carried the seat only 49-45, and Katko, who successfully cultivated a moderate image, ran far ahead of the top of the ticket by winning another dramatic 60-39 victory.

Katko spent the Trump years doing his best to distance himself from the new administration while still voting with it most of the time, a strategy that helped him win his final two terms. His opponent in 2018 was Dana Balter, a progressive activist and academic who defeated the DCCC’s favored candidate in the primary. Katko this time looked like the strong favorite early on but for once, the political climate very much worked against him.

Balter benefited late from the “green wave” that allowed Democratic candidates to raise unprecedented amounts of money as well as late spending from national groups, and she ended up giving Katko his first close race. Still, the incumbent held on 53-47, which made him just one of three House Republicans to prevail in a Trump district during that Democratic wave year.

Balter sought a rematch in 2020, and this time, it very much looked like Katko could finally lose. This became an expensive battleground early on, and Team Balter bet on a solid Biden performance at the top of the ticket to carry her to victory. Still, Team Blue got some very unwelcome news when Republicans took advantage of a paperwork error to successfully sue to keep Steven Williams, whom the liberal Working Families Party had nominated as a placeholder candidate until Democrats chose their nominee on the ballot.

Ultimately, while Biden did indeed improve on Clinton’s small win from four years before, Katko once again secured plenty of crossover voters and won 53-43, with Williams taking 4%.