WATCH: Seth Meyers explains why Trump is really just a 'puppet' beholden to billionaire donors

With President Donald Trump's former chief strategist Steve Bannon declaring open war on Republican Senate Leader Mitch McConnell, Late Night with Seth Meyers went in-depth examining billionaire hedge-fund mogul Robert Mercer and his daughter Rebekah, who are said to be the most influential big donors in the Trump era.

Meyers noted Bannon is "using the help and money of wealthy donors like Robert and Rebekah Mercer to try to push Trump's agenda by supporting fringe-right congressional and Senate candidates across the country."

Meyers explained that Robert Mercer made his billions as a hedge fund manager while his daughter Rebekah Mercer was a Wall Street trader.

"The Mercers initially supported Ted Cruz, then -- after realizing they were they were literally the only two people on earth who liked him -- threw their money behind Trump, and they've been influencing the White House ever since," Meyers suggested.

"Now, with Trump in the White House, it seems the Mercers are feeling more emboldened than ever but their targets aren't Democrats like Hillary Clinton this time, it's establishment Republicans," Meyers noted while introducing a video montage of primary saber-rattling from Steve Bannon.

Meyers noted the Mercer-Bannon support for Republican Roy Moore in the Alabama special election for the US Senate seat vacated by Attorney General Jeff Sessions.

"But they're not stopping in Alabama," Meyers noted, explaining that Robert Mercer had donated $300,000 to a SuperPAC backing Dr. Kelli Ward's primary challenge of Sen. Jeff Flake (R-AZ). On Tuesday, Flake announced he would not be seeking re-election.

"But Kelli Ward is a doctor so she can't be all that crazy, right?" Meyers asked, then looked at a picture of Secretary of Housing and Urban Development Ben Carson, before remarking, "oh, right."

"Flake is toxic? Trump's so toxic when he signs a bill it melts the pen," Meyers noted.

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