When historians look back on the early days of 2024, they probably won’t recall what, precisely, an elderly Democratic president couldn’t quite remember about the names or countries of other world leaders. They will note what 26 Senate Republicans chose to forget about world leadership.

I’m referring to Tuesday morning’s Senate vote on a $95 billion supplemental foreign-aid package, including $60 billion in desperately needed military assistance for Ukraine, along with $14 billion for Israel and $10 billion for civilians in conflict zones, including the Gaza Strip. The bill must still pass the House, where it faces the opposition of Speaker Mike Johnson and can only hope to survive via parliamentary maneuvering and the votes of Democrats plus some remaining Republican security hawks.

On paper, the 70-29 vote looks like a bipartisan embrace of embattled democratic allies. But it marks the moment when Republicans reverted to the isolationism of the original America First Committee of pre-World War II infamy. A majority of the GOP Senate conference, including onetime Ukraine hawks such as Lindsey Graham and Tom Cotton, voted against the aid — mostly, they said, because it wasn’t paired with border-security measures.

That’s the same bill they voted against last week — a bill patiently negotiated over months by one of the most conservative Republicans in the Senate, Oklahoma’s James Lankford. The cynicism would be breathtaking if it weren’t so predictable coming from the Trumpified right.

Let’s walk through some additional points of dissent among Republicans who opposed the bill.

From Arkansas’ Cotton, there’s the argument that support for Israel’s efforts to defeat Hamas is incompatible with any civilian assistance for residents of Gaza. From Wisconsin’s Ron Johnson, we have the claim that although Vladimir Putin is “an evil war criminal,” Russia is certain to win the war, so funding Ukraine prolongs Ukrainian suffering and, by implication, wastes American money. From Ohio’s J.D. Vance, this: “The supplemental represents an attempt by the foreign policy blob/deep state to stop President Trump from pursuing his desired policy.”

What a mix of cruelty, defeatism, conspiracy-mongering and political servility.

I’m surely among the most pro-Israel commentators around, but I can think of no moral or strategic argument in which hunger and disease among Gaza’s civilians serve anyone’s interests, least of all Israel’s. Johnson’s argument that Ukraine can’t win is belied by the fact that until it started running out of artillery shells, it was more than holding its own against Russia. It also echoes the prewar defeatism of figures such as Robert Taft and Joseph Kennedy, who argued against helping Britain during the Blitz because Hitler was destined to win.

As for Vance, at least his position has the virtue of clarity: This is about sucking up to Donald Trump and his followers and abetting the Republican front-runner’s declared policy of encouraging Putin to invade underspending NATO members.

What all this makes for is a deeply unserious Republican Party at a deadly serious global moment. It’s commendable that 22 Republicans still chose to vote for the bill. But many of those who did — Mitch McConnell and Mitt Romney among them — are nearing the end of their careers. Today’s GOP isolationists now have more in common with George McGovern’s “Come home, America” slogan than with anything Ronald Reagan or Dwight Eisenhower stood for.

There is abundant room to criticize the Biden administration’s foreign policy record, from the shambolic withdrawal from Afghanistan to the reluctance to arm Ukraine with the weapons it needed when it needed them (and not after the Russian army consolidated its front lines) to, yes, its disastrous performance at the southern border, which has been both a policy and a political fiasco.

But the Republican riposte to these failures reminds me of something theoretical physicist Wolfgang Pauli reportedly said about a young physicist’s work: “It is not even wrong” — that is, not even in the vicinity of a serious opinion. There is no conceivable reason the fate of Ukraine, a vital U.S. interest, should hinge on our border policy, however broken, any more than a patient should put off getting a skin cancer removed until he loses 50 pounds. It is an idiotic linkage guaranteed to do harm.

In January 1945, Arthur H. Vandenberg, R-Mich., gave a landmark Senate speech now remembered as the moment when his party finally began to put its reflexive isolationism behind it. “We still propose to help create the postwar world on a basis which shall stop aggressors for keeps and, so far as humanly possible, substitute justice for force among freemen,” he said. “We propose to do it primarily for our own sake.”

For our own sake.

The point of helping Ukraine defend itself against its despotic foe — like the point of defending Israel, or Taiwan, or NATO members rich or poor — isn’t altruism. It’s self-interest rightly understood, the kind of understanding that prewar isolationists such as Vandenberg gained only from the ashes and agony of a world war. For the GOP to now lose that understanding is as much a disgrace to it as it is, potentially, a disaster for us all.

Bret Stephens writes a column for the New York Times.