Defenders of our nation’s crummy criminal sentencing laws have relied on just two arguments for the last 20 years: Lengthy mandatory minimum sentences have caused crime to fall and have helped prosecutors persuade guilty defendants to cooperate against others.

These arguments served supporters of the status quo well because they had superficial appeal. Today, however, both arguments have been proven false, and even former defenders of the lock-’em-all-up policies have jumped ship and now back commonsense reform.

First, it simply is not true that passing mandatory minimum sentencing laws will always reduce crime and repealing these laws will increase crime. Yes, Congress and the states passed lots of mandatory sentencing laws in the mid- to late 1980s and the crime rate fell, but that is only part of the story.

A decade or so ago, many of the experts who previously supported prison-heavy policies began to think we had gone too far. Most notably, Professor Steven Levitt, author of the best-selling book “Freakonomics,” estimated in 2004 that more incarceration deserved credit for up to one-third of the crime drop in the 1990s. (Note: Even this estimate means that two-thirds of the decrease was due to other factors.)

Professor Levitt’s estimate was higher than that of many other experts, so mandatory minimum defenders cited him frequently. Eight years later, however, Professor Levitt said:

“In the mid-1990s I concluded that the social benefits approximately equaled the costs of incarceration. Today, my guess is that the costs outweigh the benefits at the margins. I think we should be shrinking the prison population by at least one-third.”

From the status quo corner, all one heard were crickets. Levitt’s new idea appeared nowhere in the tough-on-crime talking points. Of course, no one in Congress was or is proposing to reduce prison populations that much. Even the most ambitious sentencing reform pending in Congress, the bipartisan SAFE Justice Act, would not achieve that target.

Many states began to rethink their mandatory minimum sentencing schemes at the same time Levitt was questioning their utility. Michigan, once home to the toughest drug laws in the country, repealed its mandatory minimums. New York, Delaware and Rhode Island repealed most of their drug mandatory minimums, too. Over the course of a decade and a half, 30 states either repealed or reformed their drug laws. In every state, the crime rate fell, sometimes at a faster clip than it had when mandatory sentences were in place.

The evidence of the past decade proves that mandatory minimum sentences are not necessary to reduce crime. In fact, many states are finding that restoring some discretion in sentencing has allowed them to cut their bloated prison budgets and reinvest the savings in cops, investigators and prosecutors. They are finding that this approach works better.

The second argument one often hears from defenders of the current system is that mandatory minimums are needed to coerce guilty defendants to plead guilty and cooperate against other criminals. Again, the argument has intuitive appeal; who when facing a mandatory prison sentence of 10 years wouldn’t do anything in his power to avoid it?

But if this argument were correct, we would expect to find plea-bargain rates for crimes carrying mandatory minimum sentences to be much higher than the plea rates for crimes that don’t carry automatic sentences. Alas, that’s not what we find.

According to the U.S. Sentencing Commission, the plea rate for drug trafficking, which carries mandatory minimum sentences, is actually lower than the plea rates for manslaughter, larceny, robbery, embezzlement and counterfeiting, none of which carry mandatory minimum sentences. Just this week, career prosecutor and current U.S. deputy attorney general Sally Quillian Yates told Buzzfeed that the threat of a mandatory minimum sentence is not necessary to persuade a guilty defendant to cooperate.

Mandatory minimum sentencing laws can no longer be defended. That is why politicians and advocates from across the political spectrum, including President Obama, senators Ted Cruz, R-Texas, and Rand Paul, R-Kentucky, House Speaker John Boehner, R-Ohio, Koch Industries, the ACLU, the NAACP and The Heritage Foundation have come together to support commonsense reform. With modest improvements, we can ensure that violent and dangerous repeat criminals continue to get the stiff sentences they deserve while nonviolent offenders get shorter, more proportionate sentences.