Sen. Mitch McConnell, in 2005, defending the absolute right of a sitting president to nominate judges.
"The Constitution of the United States is at stake. Article II, Section 2 clearly provides that the President, and the President alone, nominates judges. The Senate is empowered to give advice and consent. But my Democratic colleagues want to change the rules. They want to reinterpret the Constitution to require a supermajority for confirmation. In effect, they would take away the power to nominate from the President and grant it to a minority of 41 Senators."
"[T]he Republican conference intends to restore the principle that, regardless of party, any President's judicial nominees, after full debate, deserve a simple up-or-down vote. I know that some of our colleagues wish that restoration of this principle were not required. But it is a measured step that my friends on the other side of the aisle have unfortunately made necessary. For the first time in 214 years, they have changed the Senate's 'advise and consent' responsibilities to 'advise and obstruct.'"
Take it from Sen. Mitch McConnell: for the Senate to block a sitting president from nominating a Supreme Court nominee—not just a specific nominee, mind you, but any nominee at all, would put the Constitution of the United States itself at stake. And he's a patriot, so he would never even consider such a thing.