"We've got an opening on the court. I think Sandra Day O'Connor made a very practical point. Let's fill the vacancy so the court can fully function and get on with it," he told CNN's Chris Cuomo on "New Day."
O'Connor, a retired Supreme Court justice nominated by Republican President Ronald Reagan, said Wednesday
President Barack Obama should name a replacement and not wait until a new president is elected in November as Republicans have argued.
"I don't agree (with Republicans)," said O'Connor. "We need somebody in there to do the job and just get on with it."
King, an independent who caucuses with Democrats, said he is surprised that some Republicans have decided to reject a nominee before even having a candidate to evaluate.
"I'm surprised people can make that judgment before they even know who the nominee is," he said. "It may be that he picks a nominee that's so eminently qualified that it would be very hard to explain a vote against him, other than politics."
King acknowledged that the Senate doesn't have to support the nominee, but thinks there should be a vote.
"Of course, we have these debates. And of course, politics are involved," King said. "The politics are important. And I'm not saying a Republican senator has to vote for whoever Obama nominates. I would never say that."
But a refusal to hold a process could leave the vacancy for more than a year and that would be "pretty troublesome," King said.
The senator, who sits on the Senate Intelligence Committee, also expressed concern about a judge's order
that Apple help the FBI break into the iPhone of one of the San Bernardino, California, shooters.
"They're asking Apple to create a key that does not currently exist. And I've got a problem with that. This is a very complicated issue," he said.
Forcing Apple to do this could set "a serious precedent" that could lead to other citizens having their privacy invaded, he said.
"Once that key is made, it can end up in the hands of hackers," King said. "There's no end to complications of this."
"I think we need to slow down and really consider the policy," he added.