This story has been updated.

President Obama dismantled Senate Republicans’ arguments for blocking a Supreme Court nominee on Wednesday, and vowed to do his constitutional duty despite critics’ attempts to stonewall his potential court nominee.

“I’m going to do my job,” Obama told reporters in the Oval Office. “I recognize the politics are hard for them [Senate Republicans] because the easier thing to do is to give in to the most extreme voices within their party and stand pat and do nothing. But that’s not our job. Our job is to fulfill our constitutional duties.”

The President also said once there is “an actual nominee” rather than “an abstraction” about filling the vacancy left by Justice Antonin Scalia’s death, the American public will get the chance to weigh that person’s qualifications.

“I think it will be very difficult for Mr. McConnell to explain how, if the the public concludes that this person is well qualified, that the Senate should stand in the way simply for political reasons,” he said. “We’ll see what happens and I think the situation may evolve over time. I don’t expect Mitch Mcconnell to say that is the case today.”

He also went on to say there is no precedent which demands a President not fill a Supreme Court seat during his last year in office, and said he’s months away from being a “lame duck.”

“It’s not in the text of the Constitution,” Obama said. “Ironically, these are Republicans who say they believe in reading the text of the Constitution and focusing on the intent of the Constitution. None of the Founding Fathers thought that, when it comes to the President carrying out his duties, he should do it for three years and on the last year stop doing it.”

The credibility of the high court is at stake, he said, as the judicial appointment process gets more difficult every year. Obama said that “deterioration” would only continue if Senate Republicans “take a posture that defies the Constitution, defies logic, and is not supported by tradition.”

Obama also said he’s spoken with lawmakers and “told them I’m sympathetic” to the political pressures they face from their constituents and the party base. He also said he thinks Republicans’ remarks about blocking a nominee are disingenuous.

“There’s not a lot of vigor when they defend the position they’re taking when they defend their point. They’re pretty sheepish about it when they make those comments,” he said.

Senate Republicans, led by Majority Leader Mitch McConnell, have said they won’t hold a hearing on any Obama SCOTUS nominee. Senate GOP leaders also recently said they wouldn’t even meet with a possible nominee.