Former special counsel Robert Mueller, in hour after hour of congressional testimony, gave this country a vivid demonstration of the kind of by-the-book, nonpartisan, unshowy demeanor that at once bolstered his credibility while diminishing that of some of his more self-aggrandizing questioners. The nation should be grateful that such public servants still exist.

Mueller restated forcefully that his report did not, as President Donald Trump has claimed repeatedly, exonerate the president. But he resisted attempts by some Democrats to get him to say that the only reason he did not charge Trump was because of a legal opinion that states a sitting president cannot be indicted. He confirmed nonetheless that Russia interfered in the election, that it benefited Trump, and that Trump's organization welcomed it and lied to cover it up. That is damaging for Trump, and no amount of tweeting that the hearing was a "disaster" for Democrats will alter it.

But those who hoped the former special prosecutor would swoop in like some avenging angel and persuade Americans of the need for impeachment were left unsatisfied. Mueller refused to go outside the parameters of his report, and in doing so, avoided becoming a pawn of either side. Yes, Mueller made clear that a president could be indicted once he leaves office. But that is theoretical and, it must be said, unlikely. While no one is above the law, there is no precedent for criminally indicting, let alone convicting and jailing, a former president.

The Constitution is clear on the remedy for a president who abuses his office. It is a political process, not a criminal one. Democrats have hard decisions to make on whether to pursue impeachment, and as Mueller's testimony showed, there will be no easy path, particularly as the election draws nearer.

And that brings us to what may have been the most important element of Mueller's testimony. Without reservation, Mueller sounded an unequivocal warning about Russian interference that should spur immediate action.

"Over the course of my career I've seen a number of challenges to our democracy," he said. "The Russian government's attempts to interfere in our election is among the most serious … . This deserves the attention of every American."

Coming from someone with the stature of Mueller, who headed the FBI under Republican and Democratic presidents and who has spent a lifetime in law enforcement, such a warning should not be taken lightly. Mueller also let it be known that the FBI continues to investigate counterintelligence regarding Russian interference.

That makes it imperative that Senate Majority Leader Mitch McConnell end his obstruction of the bipartisan election security bill and allow a vote to move forward. Minnesota fought a yearlong battle to free up election security funding. Minnesota Sen. Amy Klobuchar has tried to bring the Election Security Act to the floor, to no avail. The act would, among other things, provide backup paper ballots that are crucial to accurate, tamper-proof recounts.

Congress will continue to be divided over what to do about a less-than-scrupulous president. But it can come together on what should be common ground for any patriot — securing this nation's election infrastructure against foreign interference. Failure to do so is a betrayal of the voters elected leaders serve.