On April 27, 1998, the New York Times published an op-ed by a 48-year-old Harvard Law School professor named Elizabeth Warren. In the piece, Warren argued that a bankruptcy reform bill that was working its way through Congress would hurt middle-class families — women, in particular.

Among the readers who found Warren's case persuasive was the first lady of the United States, Hillary Clinton. So when Clinton visited Boston the next month for a Democratic fundraiser, she invited Warren to a lunch meeting.

In her 2003 book, "The Two-Income Trap," Warren recalled the first words Clinton ever spoke to her: "You must be Professor Warren. I read your op-ed in the New York Times about women and bankruptcy, and I want to talk with you."

Thus began an up-and-down relationship that has lately been more up than down and is now the subject of rampant speculation about a partnership on the Democratic White House ticket. Eighteen years after their introduction, Clinton is the party's presumptive nominee for president, and Warren is its liberal conscience (or at least half of it, alongside Sen. Bernie Sanders). The influential senior senator from Massachusetts withheld her endorsement until Thursday and then instantly became a leading candidate for vice president (according to the press, anyway).

The two women planned to meet Friday, fueling the notion that Clinton might ask one of Donald Trump's most forceful critics to be her running mate. But in May 1998, Clinton just wanted to ask Warren about that article in the Times.

Warren's account of their initial sit-down and its aftermath perfectly captures the pendulous dynamic between them. The senator describes being alternately wowed by Clinton's intellect and action, and frustrated by her political calculus — which, in Warren's eyes, took compromise too far.

Before she had taken a single bite of her hamburger, Mrs. Clinton tore into the business at hand: "I have two questions for you: How are women affected by the bankruptcy laws, and how did a woman get to be a chaired professor at Harvard Law School?"
For the next 25 minutes, I pounded Mrs. Clinton with graphs, charts and projections. She ate fast and asked questions even faster. I have taught bankruptcy law to thousands of students — some of them among the brightest in the country — but I never saw one like Mrs. Clinton. Impatient, lightning-quick and interested in all the nuances. In just half an hour, she went from knowing almost nothing about the bankruptcy system to grasping the counter-intuitive twist that single mothers were helped when their ex-husbands filed bankruptcy because these men could discharge credit card debts and use the money to catch up on their child support. I explained to Mrs. Clinton how the pending bankruptcy bill would effectively dismantle bankruptcy protections for families, forcing single mothers to compete with legions of credit card bill collectors for an ex-husband's income and making it more difficult for families to hold on to their homes.
At the end of our discussion, Mrs. Clinton stood up and said, "Well, I'm convinced. It is our job to stop that awful bill. You help me, and I'll help you."

Warren credits Clinton with staying "true to her word" -- even encouraging her husband, President Bill Clinton, to veto the bill when it eventually passed two years later. This was the lead of an Associated Press story on Dec. 19, 2000: "President Clinton vetoed legislation Tuesday that proposed the most sweeping changes in the bankruptcy law in 20 years because he said it was unfair to ordinary debtors and working families who fall on hard times."

The president's objection sounded an awful lot like the one Warren had raised in her op-ed, the one she had explained in greater detail to Hillary Clinton in Boston. The Clinton-Warren alliance seemed strong.

"But the story doesn't end there," Warren wrote in her book.

In the spring of 2001, the bankruptcy bill was reintroduced in the Senate, essentially unchanged from the version President Clinton had vetoed the previous year.
This time, freshman Sen. Hillary Clinton voted in favor of the bill.
Had the bill been transformed to get rid of all those awful provisions that had so concerned First Lady Hillary Clinton? No. The bill was essentially the same, but Hillary Rodham Clinton was not. As first lady, Mrs. Clinton had been persuaded that the bill was bad for families, and she was willing to fight for her beliefs. Her husband was a lame duck at the time he vetoed the bill; he could afford to forgo future campaign contributions. As New York's newest senator, however, it seems that Hillary Clinton could not afford such a principled position. ... Big banks were now part of Sen. Clinton's constituency. She wanted their support, and they wanted hers — including a vote in favor of "that awful bill."

Warren's charge that Clinton ultimately failed to stand up to Wall Street is essentially identical in substance to the one leveled by Sanders throughout the Democratic primary. It is also, perhaps, the reason why Warren was so slow to offer her endorsement.

If Clinton really does want Warren on the ticket, the senator's answer could hinge on whether Friday's conversation goes as well as the first one they ever had — the one about a newspaper op-ed.