Left and right, the politicians who could have asked incisive questions instead made a mess of this week’s congressional hearings on the Justice Department inspector general’s report on the Clinton email probe. Yet that didn’t stop IG Michael Horowitz from flagging some serious issues — and suggesting that plenty more grim news is yet to come.

Republicans spent their time questioning Horowitz’s claim that he found no proof that bias influenced the FBI’s conclusions on Clinton; Democrats sought to drive that point home.

Yet Horowitz’s testimony and report highlighted numerous FBI lapses in the Clinton investigation. Starting with its agents’ anti-Trump text messages — most notably, top agent Peter Strzok’s vow to “stop” Donald Trump from becoming president.

“They were using their FBI devices, sometimes at work, sometimes not at work, to speak about individuals that they were investigating,” Horowitz testified. And they “tied their discussions to their investigative work — and that’s what’s concerning.” He called such conduct “antithetical to the core values of the department.”

And he still can find no serious explanation for why the central FBI office did nothing for nearly a month after learning of the huge trove of Clinton emails discovered on Anthony Weiner’s laptop by agents in New York. Tellingly, Horowitz is clear that all the reasons cited by the decision-makers don’t hold water.

Finally, he reminded lawmakers that he still has several investigations underway: on James Comey’s actions as director, the Russia-collusion probe and the voluminous leaks by agents at every level.

When he issues those reports, perhaps the House and Senate will deign to focus on solutions, not partisan warfare.