House Majority Leader Kevin McCarthy said Sunday that Michael Bloomberg is angling to "buy" the Democratic nomination to run against President Trump in 2020.

During an interview on Fox News, the California Republican said there is "real concern" with Bloomberg.

"There is a real concern because Micheal Bloomberg, who reregistered a Democrat -- he is trying to buy the Democrat nomination to run against Donald Trump," McCarthy said.

Bloomberg, a liberal billionaire and former mayor of New York City, has approved a plan to give the Democrats at least $80 million to help Democrats retake the House, the New York Times reported over the summer. Democrats have to win 23 congressional districts to return to power in the House after the November midterm elections less than a month away.

[Opinion: Michael Bloomberg has no chance of being the 2020 Democratic presidential nominee]

Though he hasn't announced his candidacy, Bloomberg announced Wednesday that he re-registered as a Democrat, a move that could foreshadow a possible challenge against Trump in 2020.

Bloomberg was a life-long Democrat until 2001, when he ran for mayor in New York City on the Republican ticket and served three four-year terms. He had been registered as an independent since 2007, around the time of the financial crisis, but said he decided to re-register as a Democrat because he believes Democrats need to provide checks and balances to the Republican majority.