If Congress wants to reduce incarceration, why did Senate Republicans try to expand it?

Criminal justice reform was the one thing Congress was supposed to get done this term. It hasn’t, and probably isn’t going to. But there’s at least one criminal-justice bill that Senate Republicans are very keen to pass: after it failed to get cloture last summer, they’re trying again Tuesday.

It’s not what you think. This wasn’t a bill to reduce mandatory minimums, which both conservative and liberal criminal justice reformers want to do. It was a bill to increase the mandatory minimum sentence (in many cases) for the most commonly charged federal crime: illegal reentry to the United States.

Why on earth, at a time when a broad (if compromised) criminal justice reform bill written by Republican chair Chuck Grassley is available for a floor vote, did Senate Republicans take a second try that would have forced the government to build a dozen new prisons?

Some Republicans really are committed to reducing federal incarceration, even when that means they can’t be tougher on people they don’t like. For other Republicans, being tough on immigration still trumps being smart on crime.

This summer, unauthorized immigrant Francisco Sanchez allegedly killed a young woman named Katherine Steinle in San Francisco, outraging conservative immigration hawks. The outcry against unauthorized immigrants and the “sanctuary cities” that supposedly protected them led to a flurry of bills getting introduced in both the House and Senate. The Stop Sanctuary Cities and Protect Americans Act is an agglomeration of the Senate contingent of those bills.

Most of the act would cut funding to cities that limit which unauthorized immigrants they turn over to federal authorities for deportation (which are often called “sanctuary cities”). Then there’s the provision championed by Sen. David Vitter (R-LA), and called “Kate’s Law,” after Steinle. That provision would create a five-year mandatory minimum sentence for any immigrant who’s convicted of illegal reentry to the US after having committed an “aggravated felony,” or any immigrant who comes back to the US after being convicted of illegal reentry (i.e., who comes back a third time).

Democrats call this “Trump’s Law,” as a way to tie congressional Republicans to the GOP presidential frontrunner’s extreme immigration views. The nickname is misleading: Trump’s immigration policy is mass deportation, and Kate’s Law wouldn’t actually cause more people to get deported. To the contrary, it would keep them in US prisons for longer before getting deported.

On the other hand, it wouldn’t have the effect that its supporters think it would, either. Senate Republicans touted Kate’s Law as a way to deter people from entering the US illegally in the future. But longer sentences generally don’t deter crime — that’s one big reason Republicans are getting on board with criminal justice reform to begin with.

Under normal circumstances, the Senate probably wouldn’t be bringing up this bill for a vote at all — much less rushing it to the floor right after getting back from a recess. But Sen. Vitter, the lead sponsor of Kate’s Law, is running for governor of Louisiana. The Republican primary in that election is Saturday. And Vitter is struggling in the polls.

It’s widely accepted in Washington that Majority Leader Mitch McConnell is bringing up Vitter’s bill for a vote so that Vitter can get a boost in the gubernatorial race. What isn’t clear is whether this is because McConnell and the rest of the Senate Republicans are doing Vitter an electoral favor because they really like him and want him to succeed, or because they really dislike him and want him to go somewhere else. Typically, you’d assume it’s the former, but Vitter’s been called “one of the most disliked members” of the Senate.

Normally this bill, like any bill, would have gone to the Judiciary Committee first before getting sent to the full Senate floor. Instead, Kate’s Law skipped the committee stage — because there was a good chance it would have been killed there.

Several Republicans on the committee, especially Sen. Mike Lee, are among the Senate’s leaders on criminal justice reform. And while Kate’s Law wouldn’t have had much impact on immigration, it would have helped expand mass incarceration at exactly the time reformers want to reduce it.

Illegal reentry is the most commonly charged and convicted crime in federal court — and it isn’t even close. In July 2015, twice as many people were convicted of illegal reentry as were convicted of the next most common crime. Right now the typical sentence is just 15 months — a quarter of the sentence under the Vitter bill.

Not all of those people would be covered by the new mandatory minimum, because some of them were entering for only the second time and didn’t have an “aggravated felony” on record (although the definition of “aggravated felony” is much broader than you’d think).

The new sentences would still apply to about 7,700 people a year, according to an American Civil Liberties Union analysis of United States Sentencing Commission data. And because their prison sentences would be far longer than a year, those increases would compound. The ACLU and the Center for American Progress estimate that within five years, there would be more than 18,000 additional people in federal prison as a result of Kate’s Law. Given how overcrowded federal prisons already are, the group further estimates that the Department of Justice would have to build 12 new prisons to house them all.

According to reports, Lee — who’s generally an immigration hawk — wasn’t willing to increase incarceration to punish unauthorized immigrants. Neither was Sen. Jeff Flake (who’s supported comprehensive immigration reform in the past). Without those two, the committee vote would have been too close for comfort. Instead, Kate’s Law was rolled into the other “sanctuary cities” bills, sent directly to the floor, and rushed to a vote this week in advance of Vitter’s election.

Admittedly, the intra-GOP split didn’t show up in the final vote. (Republican Sen. Mark Kirk voted with Democrats, but for immigration rather than criminal justice reasons.) For whatever reason, the Republican criminal justice reformers who were initially resistant to Kate’s Law weren’t willing to pick a fight over it in public.

But this is far from the last time something like this is going to happen. Criminal justice reform is like weight loss: It’s one thing to lose the pounds, but it takes constant maintenance to keep them off. There is always going to be something that one party or another sees as an urgent threat to America, and thinks Congress needs to take a stand against. And while in the abstract both Democrats and Republicans may agree that there are too many people in prison for too long, there are plenty of crimes you can name where one party or the other would say punishments aren’t harsh enough.

For criminal justice reform to work, Republican reformers have to make sure bills like Kate’s Law don’t pass — even though they want the government to be tougher on unauthorized immigration. They have to oppose massive prison expansions, even when the prisoners are people they don’t like. That’s not easy under the best of circumstances. But it’s certainly not easy in a Senate where a bill that would have forced the government to build 12 new prisons is rushed to a floor vote as a questionable favor for one senator’s gubernatorial bid.