Appearing Sunday on CNN, Democratic Rep. Adam Schiff of California said that if President Trump told Ukranian President Volodymyr Zelensky to investigate presidential candidate Joe Biden it could be grounds for impeachment.

"If the president is withholding military aid at the same time that he is trying to browbeat a foreign leader to do something illicit, to provide dirt on his presidential campaign, then that may be the only remedy that is co-equal to the evil that conduct represents," Schiff said about impeachment.

Schiff has previously said that he feels that impeaching the president is not feasible and has advocated for Trump to be "voted out." 

Speaker of the House Nancy Pelosi has been reluctant to pursue impeachment proceedings, which would have to pass the Republican-controlled Senate. She has called impeachment a "divisive measure."

"The integrity of our democracy isn't threatened when the president breaks the law. It's threatened when we do nothing about it," Rep. Alexandria Ocasio-Cortez, D-N.Y., tweeted Saturday about hesitation to impeach. 

Sen. Elizabeth Warren of Massachusetts has said that "Congress has failed to act," while former Texas Rep. Robert "Beto" O'Rourke has said that the Ukraine scandal could mean the "end of American democracy." 

An unknown whistleblower in the U.S. intelligence community has said that Trump has made a "promise" to a foreign leader on a phone. The Wall Street Journal reporting Friday that Trump pressed eight times to get Ukrainian President Volodymyr Zelensky to investigate the activities of Biden's son, Hunter Biden, in Ukraine. 

Some say that this means that Trump was using a foreign power to intervene in the U.S. elections, as Joe Biden is considered a top contender to defeat Trump in 2020.

Defenders of the president, such as Trump's lawyer Rudy Giuliani and Secretary of State Mike Pompeo, have said that an investigation is necessary and that the American people deserve to know whether Joe Biden used his position as vice president to assist his son in Ukraine.

Trump has said the whistleblower is partisan and that the scandal that has been fabricated by the "fake news media."