President Trump predicted Tuesday night that Republicans "will keep the House majority" after November's midterm elections -- and warned of dire consequences if they didn't.

Speaking to the National Republican Congressional Committee's annual March fundraising dinner in Washington, the president warned that Democrats would block efforts to secure America's borders and try to raise taxes.

"They're actually working right now to increase taxes and I'm saying, 'How do you lose to that?'" Trump said. "They want to increase taxes. Maybe they'll call that tax reform."

The president described House Democrats as being "way outside the American mainstream" and warned that they would "campaign as moderates" but "always govern as radicals."

"They are all Pelosi Democrats," Trump said, referring to the House minority leader, "weak on crime, weak on terrorism and weak on national defense."

Apart from Pelosi, Trump singled out another California Democratic congresswoman for criticism -- Maxine Waters, who he described as a "low-IQ individual."

"You ever see Maxine Waters?" Trump asked before imitating the 79-year-old. "‘We will impeach him. We will impeach him.'"

"'But he hasn’t done anything wrong,'" Trump continued in the guise of an interviewer. "'It doesn’t matter. We will impeach him.' … This is what we’re going to have to fight against."

Before Trump took the stage, the NRCC announced that the event had raised $32 million, an all-time record.

Democrats must make a net gain of 24 Republican seats to win a majority in the 435-member House of Representatives. A special election in Pennsylvania's 18th congressional district remains too close to call.

The Associated Press contributed to this report.