WASHINGTON – In his latest attack on Democrats running against him in 2020, President Donald Trump is now defending the constitutional mechanism he once opposed, the very thing that got him elected in the first place.

The Electoral College.

"The Democrats are getting very 'strange.'" Trump said during a late night tweet storm on Tuesday. "They now want to change the voting age to 16, abolish the Electoral College, and Increase significantly the number of Supreme Court Justices. Actually, you’ve got to win it at the Ballot Box!"

Trump zeroed in on Democratic calls to eliminate the Electoral College, the key to his election; while losing to Hillary Clinton by more than 3 million popular votes in 2016, Trump won enough states with enough electoral votes to prevail.

His comments come after Sen. Elizabeth Warren, who seeks the 2020 Democratic nomination, called for the end of the Electoral College in a Monday town hall.

"My view is that every vote matters," she told a crowd in Mississippi. "And the way we can make that happen is we can have national voting, and that means get rid of the Electoral College."

Former U.S. Rep. Beto O'Rourke, D-Tex., has also said that eliminating the Electoral College might be a good idea "because you had an election in 2016 where the loser got 3 million more votes than the victor."

Both Trump in 2016 and George W. Bush in 2000 won the Electoral College while losing the popular vote.

Democrats who want to change the system say the Electoral College forces candidates to focus on a limited number of battleground states, while ignoring those where one party dominates the presidential vote.

Trump claimed a popular vote election would further restrict campaigning, confining candidates to the biggest states.

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"The brilliance of the Electoral College is that you must go to many States to win," he said during his series of tweets. "The Cities would end up running the Country. Smaller States & the entire Midwest would end up losing all power - & we can’t let that happen."

Of course, Trump himself used to oppose the Electoral College, once calling it a "disaster for democracy."

Now, after his 2016 electoral victory, things have changed.

"I used to like the idea of the Popular Vote," he tweeted, "but now realize the Electoral College is far better for the U.S.A."

It would take a constitutional amendment to eliminate the Electoral College, which was created by the framers of the U.S. Constitution. But a group of states are looking at a way to make it moot by agreeing to award all of their electoral votes to the winner of the popular vote.