Senate Majority Leader Mitch McConnell signaled late last week that he has no intention of allowing a vote before year’s end on the First Step Act’s criminal-justice reforms. That’s a serious mistake.

At a Wall Street Journal event, McConnell (R-Ky.) claimed there’s just too little floor time left to let First Step pass, and bills to keep the government open have to come first. But he betrayed his real reason by calling the reform “extremely divisive inside the Senate Republican conference” and suggesting that more of his GOP members are undecided or opposed than in favor.

That last claim may prove untrue, since Sen. Ted Cruz switched to supporting First Step on Friday after sponsors made some changes he’d requested, and other fence-sitters will likely follow — especially with President Trump pushing for passage.

Then, too, supporters are still stomping out the lies promoted by the likes of Sen. Tom Cotton (R-Ark.) — charges that the bill would spring a horde of violent offenders.

In fact, as John Koufos notes, that fearmongering ignores the actual language of First Step. Worse, it pretends that the Bureau of Prisons, and indeed the entire Justice Department chain of command, would go along with a “mass jailbreak.”

Some senators may still fear a vote for the bill would leave them open to primary challenges as “soft on crime.” That seems absurd: Along with Trump, most major national law enforcement groups, including the Fraternal Order of Police, support First Step. And several deep-red Republican states have passed their own versions of criminal-justice reform, some of them more far-reaching than this bill.

Above all, McConnell’s strategy of protecting senators from a supposedly tough vote is itself high-risk — because he’s also “protecting” his members from an achievement.

Don’t forget: The “no hard votes” approach under then-Majority Leader Harry Reid (D-Nev.) proved a disaster for Senate Democrats a few years back, because it left his members with little to boast about.

Americans, especially swing voters, expect lawmakers to actually make law. But Congress won’t be passing much for the next two years, not with one party controlling the House and the other in charge of the Senate. McConnell ought to take this bipartisan victory while he can get it.

Washington just got done gushing about how the late President George H.W. Bush didn’t let politics stand in the way of principle. Passing First Step would be one way to prove that all those speeches were more than empty words.