President Biden must go. The case is that simple. He left the 2024 campaign. He should leave the White House.

The evidence since his debate with President Trump is clear. Mr. Biden no longer has the cognitive skills to be an effective commander-in-chief. 

His withdrawal from the presidential campaign simply confirms something painfully obvious. Mr. Biden simply isn’t capable of functioning at the level of a national campaign.

Well, if you can’t function as a national candidate for president, you sure can’t function as president.

In a real crisis, Mr. Biden may freeze or collapse — and it could cost American lives or America’s future.

The American people recognize that Mr. Biden’s cognitive problems pose a danger to the country’s safety.

According to Rasmussen Reports, 61 percent of Americans see Mr. Biden’s mental decline as a threat to our national security. Some 46 percent, nearly a majority, strongly agree that his mental decline is a security threat.

The three-in-five Americans who are worried by Mr. Biden’s decay are completely right.

In a crisis, the decision-making process might not be as simple as sitting in the Oval Office and chatting with a friendly staff.

In a real crisis, the president is physically moved to a safe facility and isolated. Vice President Cheney was physically picked up and carried to the White House bomb shelter as the September 11, 2001, terrorist attacks unfolded. 

President George W. Bush was on Air Force One and the plane avoided landing for four hours to minimize the risk of a second attack focused on the president.

Mr. Biden has limited cognitive capacity even when he is well-rested and surrounded by staff and his family. How much will that degrade if he is suddenly physically moved as a crisis unfolds and surrounded by serious national security professionals?

Furthermore, we must remember that our foreign adversaries are watching Mr. Biden’s decline. They watched his collapse in the 90-minute debate. They have seen the videos of him barely able to walk to Marine One or climb the steps of Air Force One.

Our foreign adversaries may make the dangerous calculation that now is the time to take big risks while we have an essentially incapacitated leader. This is a time of growing danger for the safety of America and our allies.

Convincing Mr. Biden to resign and, if necessary, using the 25th Amendment to compel him to step down, would be a hard process. It is hard to so directly threaten a veteran politician in his eighth decade. But for the country’s safety, it must be done.

Some Republicans will object that this may give the presumptive Democratic presidential nominee, Kamala Harris, an advantage by taking to the White House her from the vice president’s residence at the Naval Observatory. This may be true. But if the safety of the nation is at stake, we have no choice.

The key issues of the campaign and the key choices for our future are the same whether Ms. Harris is vice president or president.

Nothing she can do will reverse the enormous open border disaster which she helped create. Nothing she can do will erase the painful level of inflation, which Biden-Harris policies created.

Her record is fixed as a San Francisco radical who voted to the left of Senator Sanders.

Ms. Harris’s record of participating in a disastrous foreign policy was reinforced by her decision to boycott Prime Minister Netanyahu’s speech to Congress.

For many Americans, this election will be a referendum on the Biden-Harris administration’s disasters. Ms. Harris can’t pretend she wasn’t there.

For the nation’s safety, I would rather risk a cognitively coherent Ms. Harris, with whom I disagree deeply, than continue with a cognitively compromised Mr. Biden.

It is really this simple: Joe must go.