The small group of U.S. senators publicly calling for President Donald Trump to resign in the wake of numerous sexual assault accusations now includes Sen. Bob Casey (D-Pa.).

Casey joined senators Cory Booker (D-NJ), Kirsten Gillibrand (D-NY), Sen. Mazie Hirono (D-HI), Jeff Merkley (D-OR), Sen. Bernie Sanders (I-VT) and Ron Wyden (D-OR) in saying Trump should resign amid numerous allegations of misconduct spanning several decades.

"President Trump's documented history of sexual harassment and assault should have been disqualifying during last year's election," Casey told ThinkProgress in a statement Wednesday. "His offensive verbal assault against Senator Gillibrand yesterday demonstrate he still doesn't get it. And while he should resign, we know he won't. I support a congressional investigation in order to hold him accountable for his actions."

The recent call for Trump to resign follows Sen. Al Franken's resignation and replacement and the retirement of U.S. Rep John Conyers. ThinkProgress asked Senate Democrats about whether Trump should follow the path of others who have been accused, receiving responses from the group that included Casey.

Many Democrats have said Robert Muller's investigation into Russian interference with the 2016 election should run its course before pushing for a resignation or an impeachment vote. Others are calling for a congressional investigation into the claims rather than an outright call for resignation.

The calls for Trump to resign over allegations comes just days after three accusers came together at a news conference, renewing their claims of sexual assault against the president and asking why their accounts did not have any effect on the election. A day before the accusers' news conference, Nikki Haley, the U.S. Ambassador to the United Nations, said Trump accusers "should be heard" while appearing on CBS's "Face the Nation."

Trump has continued to deny the allegations and have called the claims politically motivated. Sarah Huckabee Sanders, a spokeswoman for the White House, maintains that the American people settled the issue of the accusations by electing Trump.