Special counsel Robert S. Mueller III ultimately might conclude that there was no clear case of collusion between the Russians and associates of President Trump’s 2016 campaign. That’s still somewhere in the future. But he has already laid down a challenge to the president that no longer can be ignored.

Friday’s indictments of 13 Russians laid bare in ways the U.S. intelligence community had not previously done the lengths to which the Russians went to try to subvert the 2016 elections. Not just to sow chaos, though that was clearly a goal.

The 37-page document makes plain that the motivation of the Russians was to damage Hillary Clinton and help Donald Trump as much as possible (and to help Bernie Sanders and Jill Stein).

The details tell the story of the Russian efforts to mess with U.S. democracy, from the creation of fake social media accounts to identity theft to on-the-ground research in the United States and to the purchase of social media advertising. The efforts were large and small, from the insidious to old-fashioned dirty tricks.

Deputy Attorney General Rod J. Rosenstein announces the indictment of 13 Russians linked to a troll farm as part of the special counsel investigation. (The Washington Post)

The indictments allege the Russians communicated with unwitting members of Trump’s campaign in local communities. They sought to organize rallies. They put out false information. They paid for a demonstrator “to wear a costume portraying Clinton in a prison uniform” and wired money to someone in the United States “to build a cage large enough to hold an actress portraying Clinton in a prison uniform.” It is both comical and sinister.

For more than a year, Trump has dismissed it all as fake news and a hoax. He has accused the FBI and the special counsel of conducting a witch hunt. It has been his hobbyhorse from the moment the issue was raised, even though it was Trump as a candidate who encouraged the Russians to hack and find Clinton’s lost State Department emails and who used his campaign rallies to trumpet hacked Democratic emails that were being released by WikiLeaks during the last weeks of the campaign.

The president’s reaction Friday to the indictments was typically personal and self-exonerating. “Russia started their anti-US campaign in 2014, long before I announced that I would run for President,” he tweeted. “The results of the election were not impacted. The Trump campaign did nothing wrong - no collusion.”

The indictment document is silent on the question of whether the election was impacted. But in an election that was decided by a small number of votes in Pennsylvania, Michigan and Wisconsin, who is to say what tipped the balance?

Was it Russian efforts to trash Clinton and help Trump with false information? Was it James B. Comey’s Oct. 28 letter to Congress saying the FBI was reopening the Clinton email investigation? Was it Clinton’s failures as a candidate to project a better message and to campaign where she should have? Was it Trump’s message and his hectic and opportunistic final days of campaign schedule?

No one can say what motivated people in the end to vote the way they did. But Mueller’s indictments make clear that something happened that should alarm Americans, regardless of political allegiance. And as the nation’s intelligence chiefs told Congress last week, the Russian interference efforts will most certainly continue this year and in the 2020 election cycle.

Yet the president has long resisted every piece of evidence pointing in this direction, and as a result, he has done nothing about it. He has done nothing to gird the country against such future attacks.

Trump has tried to dismiss even the concept of Russian interference because he has taken the allegations not as a direct threat to the foundations of our democratic society but as a threat to the legitimacy of his presidency.

He won the election. He won a majority of the electoral votes. He beat the odds and defied the experts. He brought down two political dynasties (the Clintons and the Bushes). He tapped into something that conventional politicians didn’t see or understand. He is the president.

But as president, he has responsibilities beyond worrying about his legitimacy.

Only Mueller and his team know what they know so far and where their investigation is headed. He has other indictments, some guilty pleas and witnesses, both cooperative and perhaps not so cooperative. Friday’s indictments came unexpectedly and landed with considerable force. They were a statement of the investigation’s legitimacy. In the face of what is now in public view, Trump would trigger an even bigger backlash if he tried to move on Mueller and disrupt the investigation.

All of this will play out over the coming months — questions of collusion or obstruction or other areas unknown to the outside world. But Friday’s indictments were a reminder that the president cannot be frozen by resentment toward the Russia investigation, which has been going on for a long time.

It was in October 2016, before Trump won the election, that the intelligence community first officially pointed the finger at the Russians for interference. There have been subsequent reports and testimony and unanimity of conclusions about the role the Russians played — not just tried to play, but played.

In one of his last acts as president, Barack Obama took unprecedented steps, placing sanctions against the Russians, including the expulsion of 35 diplomats and the closure of two Russian compounds in the United States.

In July, Congress authorized the Trump administration to administer additional sanctions to punish the Russians. So far the administration has declined to do so, arguing recently that the law authorizing the sanctions is having its intended effect without the imposition of those new penalties.

Beyond that, congressional leaders involved in their own investigations, particularly those on the Senate Intelligence Committee, have called repeatedly for the administration to begin to take steps to prevent, to the extent possible, further interference by the Russians in the coming elections. They are leaving to Mueller the knotty questions about obstruction of justice and criminality, but they have been clear about the threat of future interference.

Trump has never forthrightly embraced the conclusions about Russian meddling. A lengthy Washington Post story in December chronicled his resistance and the reticence of his advisers on bringing up the issue. Instead, he takes the word of Russian President Vladimir Putin.

“Every time he sees me, he says, ‘I didn’t do that,’ ” Trump said in November after meeting with the Russian leader. “And I believe, I really believe, that when he tells me that, he means it.” He said he thinks Putin “is very insulted by” the charges.

Now the details of that interference are in plain sight. People can choose to believe what they want about whether what the Russians did influenced the outcome of the election. But what Mueller and company have put into public view makes it impossible to conclude that there was no interference or to think that the interference was not with malign intent.

The president has only tweeted about the new information. He has not answered a direct question about the findings, nor has he been asked what he thinks should be done about them. That responsibility falls in part to his national security team to press him to act in some way to counter the ongoing threat. The ultimate responsibility is his, and so far, he has avoided taking it. Mueller has made that much, much more difficult.