Washington (CNN) There's been an important shift over the last few days in President Donald Trump's approach to the ongoing special counsel investigation into Russian interference in the 2016 election as his rhetoric and his legal team have begun to reflect an increased focus on winning the fight for public opinion rather than cooperating with the actual probe.

For months, Trump's advisers -- political and legal -- kept him largely constrained. Yes, he bashed the Russia probe as a "witch hunt" and a hoax. And he raged behind the scenes. But, he avoided going after Mueller by name and, usually, stuck to the script in public settings by insisting there had been "no collusion" with the Russians and adding that he was eager to sit down with Mueller.

And, on Monday, he added Joe diGenova -- a conservative talking head known for his insistence that there is was an active conspiracy within the FBI to frame Trump -- to the legal team dealing with the Mueller investigation.

What's changed? It's hard to pinpoint any one thing.

The fact that the Mueller probe isn't over -- as Trump lawyers promised him it would be by now -- is likely an issue. (Mueller has set no end date for the investigation.) So, too, is the the fact that Mueller's team met with Trump's legal team last week to go over areas of interest for a forthcoming sitdown with the President. Or it may just be that Trump is finally now realizing that Mueller isn't just going to go away or fully exonerate everyone involved in the probe.

Regardless of the reason, it's clear that Trump appears to have shifted from playing nice (or at least his version of nice) to playing, um, less nice. Or, more accurately, from trying to deal with Mueller's investigation to preparing to win the public perception battle in the wake of Mueller's eventual report.

Everything Trump has done in the last 96 hours suggests that he believes the idea of keeping the gloves off Mueller hasn't had any effect. (It's not clear why he would think that other than because his lawyers and advisers used that carrot to keep Trump from savaging the special counsel to this point.)

And so, with that strategy failing, Trump has returned to what he knows best -- the knock-the-crap-out-of-'em approach to politics (and life). He might not be able to stop Mueller but he sure as hell can influence what people think of him and, by extension, whatever Mueller winds up finding out.

If Trump's base believes Mueller is nothing but a secret Democrat -- he's not, he's a Republican appointed as FBI director by President George W. Bush -- then whatever comes out of the Russia probe can (and should) be discounted.

Given that Trump has no idea what Mueller will ultimately find, knocking down Mueller's credibility is a necessity. It's Trump's insurance plan. If Mueller is discredited, then whatever he finds out is disqualified in the eyes of Trump's most loyal supporters.

Will that strategy work for the broader populace? Polling suggests that more people have a positive image of Mueller than have a negative one but that large numbers don't know enough about the former FBI director to form an opinion.

That lack of knowledge about Mueller could be fertile ground for Trump. Working against him is the fact that so many people who nay have no opinion about Mueller have a strongly negative one about the President. For some (many?) people in the country, Trump attacking someone is all the reason they need to support the attackee.

It's not clear to me, however, that Trump is terribly concerned what the general populace cares about as it relates to the Mueller investigation -- or much else. From the start of his presidency, Trump has played to his conservative base at every turn. There's absolutely no reason to suspect that strategy will change now.

In short: Expect Trump to go harder after Mueller and his team. A lot harder.