At a fundraiser in the Hamptons this weekend, Senator Kamala Harris (D-CA) told wealthy donors she has “not been comfortable” with the Medicare-for-All proposal pushed by Sen. Bernie Sanders (I-VT), one of her leading rivals in the primary.

"I think almost every member of the United States Senate who's running for president and many others, have signed on to a variety of plans in the Senate. And I have done the same," Harris said, according to remarks provided by her campaign. "[A]ll of them are good ideas, which is why I support them. And I support Medicare for All. But as you may have noticed, over the course of the many months, I've not been comfortable with Bernie's plan, the Medicare for all plan."

The comments are the latest reflection of the turbulence that the California Democrat has encountered while navigating the politics of health care reform. Just two years ago, Harris was comfortable enough with Sanders’ bill to become the first senator to co-sponsor it. And back then, she exhibited no discomfort in doing so.

“This is about understanding, again, that health care should be a right, not a privilege. And it's also about being smart," Harris said in August 2017.

“So it's not only about what is morally and ethically right,” Harris argued. “It also makes sense from a fiscal standpoint, or if you want to talk about it as a return on investment for taxpayers.”

At the time, Harris’ announcement was hailed as a shrewd reading of the direction of the Democratic Party on health care—one that would boost the senator’s progressive cred ahead of a possible White House run. And as recently as April of this year, Harris' office sent a press release saying she had joined Sanders to formally introduce the Medicare-for-All Act of 2019. “Medicare for All finally makes sure every American has affordable, comprehensive health care,” she said.

That the senator now has reservations about the legislation was not, her campaign argued, a matter of political convenience but, rather, the end product of having worked on the issue more.

"There’s a difference between signing onto a good idea and running on a plan,” said Harris campaign spokesman Ian Sams. He noted that Sanders is running on Medicare-for-All but was nevertheless a sponsor of a bill from Sen. Brian Schatz (D-HI) to establish a public option. “Senator Harris was hearing from lots of voters real concerns, specifically about proactively abolishing private insurance, the four-year transition, middle-class tax hikes, and so she came up with her own plan to adjust for those that, frankly, is better than his,” said Sams.

Sanders did co-sponsor the Schatz legislation in 2017. But the senator is not a co-sponsor of the most recent bill. An aide explained that he took his name off the legislation because "he believes at this point we need a Medicare for All system. It's not like he opposes [a public option]. It's whether he is putting his name and stamp on it."

Harris’ formal health care plan differs from the Sanders’ model in a variety of ways. It aims to phase in Medicare-for-All over the course of a decade—as opposed to four years—and allow private insurers to offer plans through Medicare if they comply with strict government rules. Her plan also eschews some of the revenue-raising measures proposed by Sanders, by declining to hike middle-class taxes in order to fund health care coverage.

The Sanders campaign has slammed Harris’ plan as a contrived half-measure and one that would leave full implementation to her presidential successor. And on Monday, Sanders signaled that Harris’ Medicare-for-All slight in the Hamptons may figure into their broader case against a top rival.

“Yes, a very strong way to show consistency is to [checks notes] tell your big donors in the Hamptons that you are suddenly opposing the bill you’ve co-sponsored,” tweeted Sanders aide David Sirota.