A Republican senator said the four senators running for president should recuse themselves from President Trump’s impeachment trial.

Sen. Marsha Blackburn of Tennessee said the 2020 candidates should step back from the process because they have “unparalleled political interest” in removing Trump from office.

[Related: Impeachment set to leave Buttigieg as only top-tier 2020 Democrat campaigning full time]

Sens. Bernie Sanders of Vermont, Elizabeth Warren of Massachusetts, Amy Klobuchar of Minnesota, and Michael Bennet of Colorado are likely to leave the campaign trail as they hear the case against Trump, who was impeached for his conduct toward Ukraine. The trial could take place up to six days per week and overlap with the Iowa caucuses on Feb. 3, the New Hampshire primary on Feb. 11, and several Democratic debates scheduled for next month.

“To participate in this trial would be a failure of the oath they took to be an ‘impartial justice according to the Constitution and laws.’ Their presidential ambitions prohibit their ability to view this trial through an objective lens,” Blackburn said in a statement.