President Trump presented an increasingly well-honed campaign message Monday, saying he believes Republicans will win midterm elections in November because the U.S. would "end up being Venezuela" if Democrats flipped control of Congress.

Trump has used the line at many recent rallies as he campaigns for Republican candidates across the country.

"I think a lot of Democrats are going to vote Republican because I have many friends that are Democrats," Trump told reporters on the South Lawn of the White House on Monday.

"The main base of the Democrats have shifted so far left that we'll end up being Venezuela. This country would end up being Venezuela," he said. "I think a lot of Democrats are going to be voting Republican on November 6."

Trump has likened Democratic policies such as government-run single-payer healthcare to reforms in the South American nation that led to severe poverty and an exodus of refugees.

Trump was addressing a question about whether he was concerned that energized Democratic voters will hurt Republican candidates.

Recent polling data from Fox News indicate that Republicans may be closing an enthusiasm gap with Democrats ahead of the midterm election, in the wake of the contentious Supreme Court confirmation battle for Justice Brett Kavanaugh.