If no one seems to care that Elizabeth Warren has made her candidacy for president semi-official, let it also be said that no one seems to care that Joe Biden is about to do the same. As the public’s attention starts to focus on the primaries of 2020—God, didn’t we just do this?—many Democrats are acting as if Donald Trump, who’s having a good day when his approval ratings stay in the 40s, would beat most of the field. Maybe that’s because they’re still recovering from the shock of 2016. But maybe it’s more serious than that. If today’s Democrats can’t beat Trump, then maybe Hillary Clinton wasn’t as bad a candidate as her critics claimed. And if Clinton wasn’t the problem, then what was the problem? Such questions are behind a recent spike of debates on the left over Barack Obama’s record. More and more voices seem to be saying, either obliquely or bluntly, that Obama was a bad president.

Certainly, almost anyone on the left will agree that Obama was preferable to his Republican opponents. If they object to how Obama handled issues such as health care, finance capitalism, immigration, economic stimulus, trade, or war and peace, it’s not because they feel a Republican president would have been better. That makes it tempting to say that Obama is being criticized only for pushing insufficiently to the left, settling for the Affordable Care Act rather than Medicare for All or a stimulus package under a trillion dollars rather than one twice that size. But such an explanation tends to assume a difference of degree rather than kind, with Obama dwelling in a more purplish spot than his bluer critics. In reality, the categories that matter as much as left and right are those of establishment and radical. Obama’s record of siding reliably with the former at a time when the zeitgeist had come to favor the latter is the source of much of the tension over his legacy.

The categories of establishment and radical are tricky to define, except to say that the former wishes to preserve much of the status quo, while the latter seeks more fundamental change. If one side is full of people with opinions on how to set the dials, the other is full of people who say we need a new instrumental panel. This creates interesting alliances of left and right, ones that are less a union of extremes—a product of what political scientists call “horseshoe theory”—and more a union of dissent. A radical is not an extremist, necessarily. It’s someone who believes the fundamentals are flawed.

Many of the disputes between today’s establishment and its radicals are merely continuations of where we were about 25 years ago. When Bill Clinton intervened in the war over Kosovo, in 1999, the establishment center supported him, while the outer bands of right and left opposed it. Similarly, trade agreements such as NAFTA in 1993 and GATT (General Agreement on Tariffs and Trade) in 1994, passed on the strength of a broad center, while Democrats and Republicans on the edges voted no. On immigration, the center took a high-influx view while the disruptors took a more restrictive one. On business policy, the establishment center supported things like the Export-Import Bank of the United States, while the left and right radicals deplored it as a special interest or, as a candidate named Barack Obama would one day put it, corporate welfare.

Several factors reduced the urgency of these divisions for about a decade. One was blistering economic growth in the late 1990s. Another was a reasonably harmonious world. Then came 9/11, which reshuffled everything but also caused the right (with plucky exceptions such as Ron Paul and the founders of The American Conservative) to put aside internal disputes and, for the most part, fall in line behind George W. Bush. After the failures of Iraq and other Bush policies, though, the divisions roared back to life. If there was a crystallizing moment, it was when Wall Street as we knew it was about to collapse. In the eyes of the establishment, left and right, an unforeseeable real-estate crash had threatened the survival of the country’s vibrant financial sector and, with it, the wallets and neighborhood A.T.M.s of every American. In the eyes of the radicals, our financial sector was an out-of-control predator built on a rotten edifice that was finally about to crumble. Its collapse wasn’t the threat; it was the cure. For the first time in years, an immense policy question was breaking out not between parties but within them. Among both Democrats and Republicans, an establishment wing was supporting the bailouts, while the radical wing was opposing them.