Newt Gingrich has a message for the GOP in Washington: Start taking Donald Trump seriously.

Appearing on Fox News after Trump's Saturday win in South Carolina, the former speaker of the House argued that "nobody" in the Washington Republican political class "should kid themselves" about Trump's chances any longer.

"It is a huge night for Donald Trump and nobody should kid themselves. Here's a guy who seven months ago for the first time entered electoral politics, has learned at an extraordinary rate," Gingrich said, pointing to his second-place finish in Iowa and victories in New Hampshire and South Carolina.

"By any reasonable standard, this is a decisive victory," Gingrich continued, adding that Trump is likely to win in Nevada on Tuesday. "What people need to get a grip on in the Washington establishment is their job is to understand Trump. His job isn't to understand them. They live in a world of ideas and details and policy programs and long papers and conferences and ideas. This guy lives in a world of making very big decisions, doing very big things, and I think you could start keeping a list."

"It's a very simple rule — if you think Washington is so sick you want someone to kick over the kitchen table, then you like Donald Trump and you frankly don't care about the details," Gingrich added.

Gingrich, who won the South Carolina primary in 2012 over eventual nominee Mitt Romney, also gave the real estate mogul a few tips before he heads off for Nevada and states voting on Super Tuesday.

"First of all, change nothing between now and Nevada because it's too short of time. Hold every possible rally in Nevada you can get to and get to every small town you can get to where they never see a candidate, and you'll win Nevada in a huge margin," Gingrich said. "Then take a deep breath, take 24 hours off the campaign trail, and think about being a potential president rather than a potential candidate, and he will begin to grow into a job vastly more humbling and vastly more challenging than anything he has ever dreamed of."