President Trump is facing the worst treatment of any president dating back to George Washington, Senate Majority Leader Mitch McConnell said Monday as he urged Democrats to drop their various blockades.

For decades, presidents got all their Cabinet members approved on their first day in office, and since Watergate no other president has had so few nominees approved two weeks into his tenure.

Just as telling, every single one of Mr. Trump’s nominees has faced some opposition — for the first time in at least 40 years.

“It’s a historic break in tradition, a departure from how newly elected presidents of both parties have been treated in decades past,” Mr. McConnell, Kentucky Republican, said as he took to the Senate floor.

Only a handful of Mr. Trump’s nominees have been approved so far. By contrast, both Presidents Obama and George W. Bush got seven nominees approved in the hours immediately after inauguration, and by this point had at least a dozen in office.

Democrats say the blame lies with Mr. Trump, who they say has picked a Cabinet far outside the norm.

On Monday, Democrats were mounting a filibuster to try to sink Betsy DeVos, Mr. Trump’s pick to head the Education Department, saying she was incompetent and ideologically incompatible.

Senate Minority Leader Charles E. Schumer, New York Democrat, called two Republicans “profiles in courage” after they announced last week that they would defect on the DeVos vote, opposing her confirmation.

But that will still likely leave a 50-50 deadlock that Vice President Mike Pence will break, confirming Ms. DeVos.

“Now is the time to put country before party,” said Mr. Schumer, urging Republicans to break with Mr. Trump.

Mr. McConnell, though, countered that it was Mr. Schumer who was chasing after his party’s left wing, staging objections in order to appease liberal pressure groups.

“The Democratic leader and his colleagues are under a great deal of pressure from those on the left who simply cannot accept the results of a democratic election,” Mr. McConnell said.

“Unfortunately, many of our friends across the aisle have given in to these groups’ calls for obstruction.”