White House Chief of Staff Ron Klain wrongly claimed Monday that Joe Biden was the first president since John F. Kennedy in the early 1960s to see his party gain Senate seats in a midterm, forgetting that Donald Trump pulled off the feat just four years ago.

During an appearance on MSNBC’s "The Last Word with Lawrence O’Donnell," Klain was asked what it was like at the White House when they learned the Democrats had retained control of the Senate. 

"Well, I mean obviously it was enormously significant," Klain said. "Historically this is something that no president has done since John F. Kennedy—to hold Senate seats and potentially even go up one Senate seat, depending on the outcome in Georgia."

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Klain went on to call it an "unbelievable moment," and a win for Biden that would enable him to have an easier time confirming judicial nominees.

However, Klain appeared to be misinformed with regard to the historic nature of retaining Senate control under a president of the same political party. In 2018, then-President Trump saw his GOP-controlled Senate increase their majority over Democrats, although Democrats netted more than 40 seats in the House to take control of that chamber.

After 2016, Republicans held a 52-48 majority over Democrats, before dropping a seat in 2017 after Democrat Doug Jones was elected in Alabama. This majority was increased in 2018, with GOP wins over Democratic incumbents in Florida, Indiana, Missouri and North Dakota, while Democrats scored pickups in Nevada and Arizona. After the midterms, Republicans controlled 53 Senate seats for a net gain of two that year.

Also, in 2002, Republicans gained two U.S. Senate seats, as well as eight House seats, in the first midterms under President George W. Bush.

The White House did not respond to Fox News Digital when asked for comment on Klain’s claim, who may have misspoke and meant to say Biden was the first "Democratic" president to pull off the feat since Kennedy in 1962. O'Donnell, a strong Biden supporter, repeatedly touted Klain during the interview as the most successful Democratic Chief of Staff since 1962, the year Kennedy's Democrats pulled off the feat.

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Democrats clinched the majority this year after Sen. Catherine Cortez Masto, D-Nev., narrowly defeated Republican challenger Adam Laxalt. 

Despite Republicans’ inability to take control of the Senate, Republicans say Senate Minority Leader Mitch McConnell, R-Ky., has strong odds of keeping his post as GOP leader of the chamber.

Democrats now hold 50 seats compared to the 49 seats held by Republicans, with one seat yet to be decided in Georgia. A runoff election will be held between Republican Herschel Walker and Democratic Sen. Raphael Warnock on December 6.

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Even if Walker were to win in Georgia, Democrats would still have control with Vice President Kamala Harris's tie-breaking vote.

Fox News’ Tyler Olson and Andrew Mark Miller contributed to this report.