It is a serious offense to lie to Congress — except when Congress doesn’t care.

The leaders of the 115th Congress couldn’t care less. In Majority Leader Mitch McConnell’s Senate, there’s no penalty — not even a mildly worded reproof — when Cabinet nominees lie under oath. So, with both frequency and impunity, President Trump’s nominees have sworn oaths to tell the truth, broken them and then sworn oaths to protect the Constitution.

That’s not reassuring.

While some of the prevarications probably don’t rise to the level of perjury — and legal scholars are debating whether a senator who lies under oath is protected by the speech or debate clause of the Constitution — they are lies in layman’s terms.

To recap:

· Attorney General Jeff Sessions told the Senate Judiciary Committee that he never met with any Russian officials while he was working to elect Trump. He issued the lie proactively, as part of a dodge on the question of whether any Trump administration officials were in contact with the Russian government. Now, the Justice Department acknowledges that Sessions met with the Russian ambassador twice, and it appears there was at least a cursory discussion of the 2016 presidential election. Sessions has recused himself from any investigations involving the Trump campaign and the Russian government, but not from those pertaining to the administration. And he insists that he didn’t knowingly give the Senate false information.

· EPA Chief Scott Pruitt told the Senate Environment and Public Works Committee that he never used private email to do state business when he was Oklahoma’s attorney general. “I use only my official OAG email address and government-issued phone to conduct official business,” he said during his confirmation hearing. Turns out that Pruitt used a private email account to do some of his state work. He’s lucky that no one ever gave him classified information.

· Secretary of State Rex Tillerson told the Senate Foreign Relations Committee that he never lobbied on Russia sanctions when he was ExxonMobil’s chief. Senator Bob Corker (R-Tenn.), the chairman of the committee, reminded Tillerson that he had lobbied Corker on the issue. Now, the definition of lobbying can be parsed — it’s certainly possible that Tillerson simply called to apprise Corker of what negative effects sanctions would have on ExxonMobil’s business interests (which may not count as lobbying technically but sure sounds, smells and feels like it).

· In written responses to questions, Treasury Secretary Steve Mnuchin told the Senate Finance Committee that his company didn’t robo-sign documents when he ran it; court records and testimony suggest that’s not true.

· Secretaries Tom Price of Health and Human Services and Betsy DeVos of the Education Secretary also shaded the truth in their testimony.

Whether they perjured themselves or not, they all told lies in layman’s terms. And McConnell’s letting them get away with it.

Our system was designed with an expectation that each of the branches of government would guard their power jealously, not roll over for each other. One of McConnell’s roles is as party leader, and he’s played it well in shepherding a rogues gallery of unfit Cabinet nominees to confirmation. But it is also McConnell’s job as the leader of the Senate — and as someone who swore an oath to “support and defend” the Constitution — to demand that executive branch nominees and officials tell the truth when they testify before his committees.

By failing to enforce the Senate’s power to compel honest testimony, he is depriving the public of a critical check on the president. Republicans and Democrats who love this country understand that is more important at this moment than at any time in their lives.

But, so far, McConnell has shown no interest in guarding his institution’s prerogatives — those bestowed by the people — against encroachment by the White House and its agents. McConnell has an opening to show character here. There has to be a sanction for Cabinet secretaries who lie under oath — especially during confirmation hearings designed to vet them. At the very least, McConnell should address this Trump-era phenomenon publicly, instead of cowering from reporters when his friend, Sessions, is under the microscope.

Sessions’ lie was most unforgivable, and most deserving of a response from McConnell, for three reasons: He is a senator and should have respect for the authority of the committee on which he once sat; he was nominated for attorney general, which means he needs to have a higher degree of fidelity to the law than anyone in the country; and his lie involved his interactions with officials from a country that actively sought to undermine the last presidential election.

Sessions’ decision to recuse himself doesn’t address his rank dishonesty. There is no excuse for his behavior, and it is McConnell’s responsibility to make sure that it doesn’t stand. In addition to speaking out against lying to Congress, McConnell might want to think about legislative sanctions such as cutting the office budgets for secretaries who don’t tell the truth.

If nothing is done, McConnell’s oath of office is as meaningless as the oath Sessions took when he promised to tell the truth to the Judiciary Committee.