In 1970, when New York passed the most permissive abortion law in the country, its state senate and assembly were controlled by Republicans, and the governor was a Republican, too. It was that law that Shirley Chisholm, a Democrat and the first black woman to run for the presidential nomination of a major party, was defending in the rally in 1972 that I mention in the Lexington column this week. 

I found myself reflecting on the history of that abortion legislation as I read through our package describing the policy agendas of the Democratic and Republican candidates for president this year. Taken together, as our leader says, the articles reveal at least as much convergence as differentiation between the candidates—convergence on industrial policy, trade, entitlements, immigration, fracking and foreign policy that represents big changes in core partisan positions of not long ago. 

We shouldn’t be surprised. Parties are always in process, sometimes radically so. Today, we might think of Democrats as united in favour of abortion rights, Republicans as opposed. But after more than five hours of agonised debate in the New York state senate on March 18th 1970, the majority that passed the abortion law consisted of 13 Republicans and 18 Democrats. The bill moved to the assembly, where the vote deadlocked, 74 to 74. But before the clerk could bring down the gavel, George Michaels, a Democrat from central New York, asked to be recognised. 

He had voted no. But in a trembling voice, with tears in his eyes, he said one of his sons had called him a whore. Another son had implored him not to be the vote to sink the bill. “Mr. Speaker, I fully appreciate that this is the termination of my political career,” Michaels said. “But what’s the use of getting elected or re-elected if you don’t stand for something?” He switched his vote, then dropped to his seat and lowered his face into his hands. Constance Cook, the Republican assemblywoman who co-sponsored the legislation—one of just four women out of 207 legislators in the two chambers—embraced him. 

Michaels would indeed lose his seat to an opponent of abortion, as would some others who voted for the bill. He would never hold elective office again.

Two days later the governor, Nelson Rockefeller, signed the bill into law. “The wives of the senate and assembly put this bill through,” he said. The new law permitted abortions within 24 weeks of pregnancy, or whenever a mother’s life was in jeopardy. In 1972, the legislature voted to repeal the law, but Rockefeller vetoed that legislation. Then in 1973 the Supreme Court issued Roe v Wade, modelled in part on New York’s standards.

Yes, Rockefeller was a different kind of Republican, one who would be repelled by and rejected by today’s party. That’s the point. The insanity of this campaign season, the intensity of Donald Trump’s deranging style of politics, may be distracting attention from deeper shifts under way. This much policy change is significant, obviously, but, even more interesting, this much policy overlap makes little sense. Even on abortion, Mr Trump is scrambling to blur the difference (abetted, it would seem, by his wife, Melania). 

The parties appear destined over time to sort themselves into new coalitions defined by more sharply delineated agendas. Assuming the republic survives—and I choose to assume it will—that seems sure to be the most important political story of the coming years. I just hope at least some of the politicians who determine the coming shifts are as courageous about doing the right thing, in the end, as Michaels was. 

As I mentioned earlier, this week we published a series of eight briefs focused on the policy issues that we believe are the most important to America’s upcoming election. Read them here:

If you have any thoughts on the abortion divide in America, or the policy issues most crucial to the election, write to me at jbennet@economist.com.