From now on, the Trump-Russia affair, the investigation that dominated the first years of Donald Trump's presidency, will be divided into two parts: before and after the release of the Mueller report. Before the special counsel's findings were made public last month, the president's adversaries were on the offensive. Now, they are playing defense.

The change is due to one simple fact: Mueller could not establish that there was a conspiracy or coordination between Russia and the Trump campaign to fix the 2016 election. The special counsel's office interviewed 500 witnesses, issued 2,800 subpoenas, executed nearly 500 search-and-seizure warrants, and obtained nearly 300 records of electronic communications, and still could not establish the one thing that mattered most in the investigation.

Without a judgment that a conspiracy — or collusion, in the popular phrase — took place, everything else in the Trump-Russia affair began to shrink in significance.

In particular, allegations that the president obstructed justice to cover up a conspiracy were transformed into allegations that he obstructed an investigation into a crime that prosecutors could not say actually occurred. Although it is legally possible to pursue an obstruction case without an underlying crime, a critical element of obstruction — knowledge of guilt — disappeared the moment Mueller's report was released.

Of course, TV talking heads are still arguing over obstruction. But with the report's release, the investigation moved from the legal realm to the political realm. And in the political realm, the president has a simple and effective case to make to the 99.6% of Americans who are not lawyers: They say I obstructed an investigation into something that didn't happen? And they want to impeach me for that?

The ground has shifted in the month since the report became public. Before the release, many Democrats adopted a "wait for Mueller" stance, basing their anti-Trump strategy on the hope that Mueller would find the much-anticipated conspiracy.

Then Mueller did not deliver. And not only that, Mueller's report stretched to 448 pages, with long stretches of minutia and arcane legal argument that the public would never read. Democrats searched for a way to convince Americans that the president was still guilty of something serious.

They devised a plan to turn the Mueller report into a TV show, accessible to millions of viewers who have not read even a page of the report itself. They would call key witnesses to give dramatic testimony in televised hearings that would build support for possible impeachment.

At the same time, they would insist that Attorney General William Barr, who has allowed top lawmakers to see the full Mueller report with the exception of a small amount of grand jury material, was hiding something, and that the hidden material might reveal presidential wrongdoing.

So far, the strategy has not worked. The White House, which provided Mueller testimony and documents that might easily have been withheld as privileged, has not been so forthcoming with Congress. We gave the criminal investigator, Mueller, what he needed, the White House said, but we are not obligated to do the same for Congress.

The dispute could take a long time to settle.

In the meantime, House Democrats have been reduced to stunts to try to grab the public's attention. At the Capitol recently, they enlisted Hollywood star John Cusack to take part in a public reading of the entire Mueller report — it took 12 hours — as C-Span cameras rolled. The event did not exactly captivate the nation.

Now, Republicans have turned the tables on Democrats by pumping new energy into their long-held desire to "investigate the investigation." Barr, who set off enormous controversy with his statement that "spying did occur" against the Trump campaign, has taken up the cause, assigning U.S. attorney John Durham to look into the origins of the probe.

Anticipation is also building for the release of Justice Department inspector general Michael Horowitz's report on the department's handling of the case. It is probably not a coincidence that some Obama-era intelligence figures are now pointing fingers at each other over their reliance on the so-called Steele dossier, a collection of unsubstantiated allegations against the president compiled by a former British spy on behalf of the Hillary Clinton campaign.

None of this would have happened without the Mueller report's conclusion that the evidence did not establish conspiracy or coordination. If Democrats could still claim that Trump and Russia conspired in 2016, they would still have the upper hand. But after Mueller, that claim is no longer possible, and Democratic hopes are dwindling.