DES MOINES — (CNN) Iowa’s top executive became the longest-serving governor in American history on Monday — and the 2016 GOP field took note less than 50 days before the key state votes in the caucuses.

Republican Gov. Terry Branstad served his record 7,642nd day in office Monday, nearly 21 years, according to The Associated Press.

And the longevity is especially noticed by the Republican candidates hoping to win Branstad’s state’s caucus in February — the first votes cast in the primary in the nation.

Politicians used social media to congratulate the popular governor Monday, as they campaign heavily in the state.

“Congrats to Iowa’s @TerryBranstad as he becomes the longest serving governor in U.S. history today! -John #iacaucus,” Ohio Gov. John Kasich tweeted, with a picture of himself and the governor.

“Congratulations to @TerryBranstad for becoming America’s longest serving governor,” said Rick Santorum, who narrowly won the Iowa caucus in 2012 despite losing his bid for the GOP nomination.

Florida Sen. Marco Rubio’s spokesman noted the anniversary on Twitter, as well.

“Good read: AP’s @catherine_lucey profiles @TerryBranstad as he nears historic record as longest serving Gov ever,” Alex Conant tweeted.

And even though he is no longer a 2016 candidate, Wisconsin Gov. Scott Walker couldn’t let the Iowa milestone go unnoticed.

“On Mon., my friend @TerryBranstad will be the longest serving Governor in American history. Congrats, Terry!” Walker’s account tweeted.

Branstad thus far is not throwing his powerful force in Iowa behind any of the GOP candidates — though he has made his distaste for one of them apparent. Branstad told CNN last week that he does not believe Donald Trump will win his state’s caucus — despite Trump’s strength in the polls there for months.

“I think it will change between now and February 1. I have a lot of confidence in the Iowa voters in making that decision,” Branstad told CNN’s Chris Cuomo.

Recent Iowa polls have shown a shifting in the GOP race with Texas Sen. Ted Cruz taking the top spot from Trump and surging to second place in others. Ben Carson, meanwhile, has seen his support in the state fade after a surge to threaten Trump in early fall.

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