Republican presidential candidate Bill Weld said Monday on MSNBC that President Trump's phone call with Ukrainian leader Volodymyr Zelensky in July amounted to "treason." During the call, Trump reportedly pushed Zelensky to investigate the activities of Joe Biden's son Hunter in Ukraine.

"Talk about pressuring a foreign country to interfere with and control a U.S. election. That's not just undermining democratic institutions. That is treason. It is treason pure and simple, and the penalty for treason under the U.S. code is death," Weld said.

Weld, a former U.S. attorney and governor of Massachusetts, continued by saying that the Constitution would penalize Trump by removing him from office.

Max Boot, a right-leaning columnist for the Washington Post, tweeted that "I love Bill Weld and appreciate his outrage (wish there was more of it among Republicans) but I don't think that talking about treason and execution is helpful. Let's stick to impeachment."

Journalist Andrew Feinberg said Trump likely hasn't committed treason, as Ukraine is not considered an enemy of the U.S.

Several Democratic politicians, such as Rep. Alexandria Ocasio-Cortez of New York and Sen. Elizabeth Warren of Massachusetts, have called for Trump to be impeached over the scandal.

Trump has said that the scandal is a fabrication by the "fake news media." Defenders of the president, such as Secretary of State Mike Pompeo, have said that Americans deserve to know whether Hunter Biden did anything illegal in Ukraine, and if Joe Biden used his position as vice president in 2016 to protect his son from investigations from the Ukrainian authorities.

Weld, along with former Illinois Rep. Joe Walsh and former South Carolina Gov. Mark Sanford, are all attempting to run against Trump in the Republican primary. All three are longshots for the nomination, especially since some states are choosing to not hold Republican primary contests.