Fox News prime-time host Tucker Carlson thinks President Trump "could lose" his reelection bid because 2020 Democrat Sen. Bernie Sanders may hold a competitive edge over him.

"No matter what happens, nobody is going to win this election in a national landslide. Those don't happen anymore. Trump could lose. Will he lose? Well, that depends entirely on what he runs on," Carlson said on his show Monday night.

Carlson, 50, explained that Trump was successful as an "insurgent" candidate but said the president had yet to fulfill his "Make America Great Again" slogan.

"Things are a lot better in a lot of ways, but they're not fixed," Carlson said.

The Fox News host went on to say that because Republicans have fallen short, socialist Sanders, 78, will be able to "win many thousands of voters who went for Donald Trump" in 2016 if he secures the party's nomination in 2020.

"The candidate who makes it easier for 30-year-olds to get married and have kids will win the election and will deserve to win," Carlson prefaced his warning. "Improve people's lives, and they will vote for you. Period. Republicans ought to write that on their hands."

Carlson believes Sanders's plan to forgive student loans would enable the Vermont senator to beat Trump, saying: "Debt is crushing an entire generation of Americans. Republicans need a plan to make it better, or they’ll be left behind.”

He also urged Republicans to defend traditional social values, accusing Democrats of "waging the most aggressive possible campaign against everything normal people think is virtuous" while adding that he believes Americans are "conservative in the most basic sense: They love their families above all."

"They distrust radical theories of anything because they know that when the world turns upside down, ordinary people get hurt. They don’t want to burn it down. They just want things to get better. The candidate who promises to make them better, incrementally but tangibly, will be inaugurated president a year from today," Carlson concluded.

Sanders is currently polling in second place among Democratic candidates for the White House with 20.4% support. He trails behind former Vice President Joe Biden by about 8%.

[Opinion: Bernie Sanders isn't a joke. He's dangerous]