WASHINGTON — (CNN) Retiring Democratic Sen. Barbara Boxer, who was an outspoken supporter of Hillary Clinton during the 2016 election, is set to introduce a Senate bill that aims to end the Electoral College.

Boxer announced in a statement on Tuesday that the bill, which she planned to introduce later Tuesday afternoon, would determine the winner of presidential elections by the outcome of the popular vote.

She cited President-elect Donald Trump’s victory in the Electoral College despite Democratic nominee Hillary Clinton’s apparent popular vote advantage.

“In my lifetime, I have seen two elections where the winner of the general election did not win the popular vote,” Boxer said in a statement. “The Electoral College is an outdated, undemocratic system that does not reflect our modern society, and it needs to change immediately. Every American should be guaranteed that their vote counts.”

“In 2012, Donald Trump tweeted, ‘The electoral college is a disaster for a democracy,’ ” Boxer added. “I couldn’t agree more. One person, one vote!”

According to CNN’s election results as of Tuesday, Clinton won 61,329,657 votes and Trump won 60,530,867.

This is the fifth time in history that a nominee has won the popular vote but not the Electoral College. The same situation happened to Al Gore in 2000, when he lost to George W. Bush.

The actual likelihood of Boxer’s bill passing is low. It’s a proposed constitutional amendment, which would require passage not only by two-thirds majorities in the House and Senate, but then in three-quarters of states.

A lame duck session and a Republican Congress will make it difficult to get such a bill through the legislative branch.

On Tuesday, Trump praised the Electoral College after previously criticizing the system. He said he could have won the popular vote if he campaigned differently.

Trump tweeted he would have won the populous states of Florida, New York and California if he had spent more time campaigning there.