Congress is on the brink of a first for the Trump era: the passage of a major piece of bipartisan legislation. It may also be the last.

Lawmakers have wrangled for five years over criminal-justice reform, but after months of recalcitrance, Senate Majority Leader Mitch McConnell announced on Tuesday that he would allow a floor vote on Congress’ latest effort, the First Step Act. The Kentucky Republican had appeared sympathetic to hardline opponents like Arkansas Senator Tom Cotton, but ultimately relented in the face of the bill’s broad support.

How broad? The First Step Act is supported by President Donald Trump, who enthusiastically campaigned on tough-on-crime policies, and the American Civil Liberties Union, which is waging a legal war against his administration. A coalition of prominent conservative and religious organizations also backed the legislation, as well as some high-profile law-enforcement groups. So have some liberal organizations, though many progressives have mixed feelings about the bill. The House passed a version of it in May in a 360-59 vote.

This unusual coalition is one of many reasons why the First Step Act might be the strangest piece of legislation in the Trump era. It’s both groundbreaking and meager, both heartening and disappointing—a long-overdue retreat from decades of inhumane policy, but also an insufficiently small step toward a more conscientious approach to crime and punishment.

One of the bill’s central provisions expands what’s known as the “safety valve,” which allows federal judges to ignore mandatory minimums in sentencing defendants who commit nonviolent, low-level crimes. Another provision reworks the three-strikes requirement for drug-related felonies: Instead of a life sentence, someone sentenced under it would receive only 25 years in prison. Modest though these changes are, they would not apply retroactively.