In a rebuke to the White House, Senate Republicans blocked two of President Barack Obama’s nominations on the floor, reviving a threat from Democrats to change the rules for dealing with filibusters.

The Senate voted not to consider the nomination of Rep. Mel Watt, a North Carolina Democrat, to lead the Federal Housing Finance Agency following resistance from Republicans over his qualifications.

That opposition led to a 56-42 vote — four votes short of the 60 needed — against moving the nomination process to a final debate and floor vote on Obama’s nominee to replace Edward J. DeMarco, who has been acting director since 2009.

Less than an hour later, Republicans blocked Washington lawyer Patricia Millett, the first of Obama’s three nominations to vacancies on the U.S. Court of Appeals for the District of Columbia Circuit, considered the nation’s second most influential because it hears appeals of federal regulatory cases.

The vote on her nomination was 55-38. Three Republican senators voted “present.”

The two rejections threaten to reignite the battle over presidential nominations. “This is a war on the other two branches of government and their ability to do the jobs the American people need them to do,” Sen. Jeff Merkley, an Oregon Democrat, said in a statement after the votes. “The Senate rules must change.”