Former White House Chief strategist Steve Bannon said in an interview aired Sunday that President Donald Trump will win the 2020 election "bigger than he won in 2016," but will face challenges following investigative reports.

Democrats could weaponize the Mueller report on possible Russian interference and potential collusion by Trump's 2016 election campaign, Bannon said on CBS's "Face the Nation," leading to a contentious climate for the country.

"I think that 2019 is going to be the most vitriolic year in American politics since before the Civil War," Bannon said. "And I include Vietnam in that. I think we're in, I think we're in for a very nasty 2019."

Bannon cited a strong economy among the reasons why Trump will win in 2020, despite the Mueller probe and the Southern District of New York investigation into Trump's inaugural committee. The next few months will be tough for Trump, Bannon said, but will "get him very focused" instead of putting him in a weaker position for the election.

In the Republican primary, Bannon said he thinks Trump will face an opponent from the party's center or left.

"I think it will be symbolic," Bannon said. "I don't think it will be serious."

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So far, 10 Democrats are running for president in 2020 — including Sens. Bernie Sanders, Elizabeth Warren, Amy Klobuchar, Kamala Harris, Kirsten Gillibrand and Cory Booker.

In defeating Hillary Clinton in 2016, Trump won 30 states and 304 electoral votes to win the White House. He became the fifth president elected while losing the popular vote.

Trump held his first political rally of the year in El Paso two weeks ago and has regularly tweeted about Democratic contenders.

The Mueller report is not expected to be released this week, the Justice Department said Friday, but Trump's former personal lawyer Michael Cohen is scheduled for a public hearing Wednesday before the House Oversight and Reform Committee.