With that mocking cry, delivered from the bosom of an adoring West Virginia crowd, President Donald Trump offered the most explicit glimpse yet of how he plans to cope with the spreading net of special counsel Robert Mueller's investigation.

"Most people know there were no Russians in our campaign, there never were. We didn't win because of Russia, we won because of you," Trump said at a raucous campaign rally.

The President offered a political argument -- not a legal one -- for why the Russia story was "a total fabrication" on a day of dizzying revelations about the probe, that heaped fresh pressure on his beleaguered White House.

Trump's rhetoric and behavior have often defied prediction and logic, and history suggests his comparatively moderate approach on Thursday night could yet be followed by a scorching tweet storm or an assault on Mueller's character and position.

But Trump's apparently scripted remarks in a context when he has often careened into improvisation and off the political reservation, may also be a hint that he just may be ready to take care of the politics, and let his legal team handle his defense in a case in which he insists he has nothing to hide.

Trump's defiant yet calibrated message followed significant breaking news on Thursday over Mueller's probe into allegations of collusion between Trump campaign aides and Moscow, that once again electrified Washington.

First came a report by The Wall Street Journal that Mueller had convened a grand jury in a sign that his panel is expanding and making progress.

CNN then weighed in with a special report, detailing how Mueller's team had seized on financial ties between Trump and associates and Russia as one of the best ways to drive the investigation forward.

Trump had previously warned in an interview with the New York Times that Mueller would cross a red line if he delved into his family's financial records.

Then, capping a frenzied afternoon, Reuters reported that Mueller's team had issued subpoenas in connection with the June 2016 meeting between Donald Trump Jr., top campaign aides and a Russian lawyer.

Convening a grand jury does not signal that indictments are imminent or that Mueller has concluded there has been wrongdoing. The move is often simply a tool to allow a prosecutor to subpoena evidence or testimony.

But Thursday's revelations were a sign that the former FBI director's investigation is serious, expanding and gathering pace, and will mean more complications for West Wing staff and the President himself.

Trump's answer was clear, as he previewed a political strategy designed to question Mueller's legitimacy , suggesting his investigation was a tool of the establishment that is still smarting from Hillary Clinton's election loss.

Mueller is investigating whether there was any collusion between Moscow's spies and the Trump campaign -- allegations that, if proven true, could represent an abrogation of American democracy.

But Trump, admittedly before a receptive audience, implied that any outcome of the probe that did not favor him or his associates would in itself represent a flouting of democratic norms.

"They can't beat us at the voting booths so they are trying to cheat you out of the future and the future that you want," the President told the crowd, during a vintage performance in the heart of Trump country, Huntington, West Virginia.

"I just hope that the final determination is a truly honest one which is what the millions of people who gave us our big win in November deserve and what all Americans who want a better future want and deserve."

It was not that Trump softened his stance -- his tone was caustic and highly partisan, suggesting "the prosecutors" should be investigating Clinton's missing emails. But in an unusually nuanced approach, he attacked Democrats rather than taking on Mueller head on. And he managed to make his political case in a way that did not immediately dismember and detract from the arguments of his lawyers -- a feat that he has not always achieved.

Trump's response to the day of drama was highly anticipated since it represented a first test for the new high powered political and legal team that he has assembled to defend him and relaunch his struggling presidency.

The arrivals of veteran Washington lawyer Ty Cobb as Trump's top legal counsel and new chief of staff John Kelly have been hailed by supporters as a way for Trump to steady a chaotic White House and an inconsistent legal team.

It may be significant, that while his remarks about the Russia probe on Thursday night were scathing and scornful, they did not specifically focus on Mueller himself.

And so far there have not been the kind of personal assaults against the prosecutor and others on Twitter, that often have deepened his political peril and even his legal position.

As new revelations on the Russia probe emerge, the question now is: how long Trump can keep his discipline (hold his tongue and his tweets) and will he deviate from Thursday's message or stick to its confines?

Trump's legal team responded to Thursday's reports exactly in the way that might be expected of a conventional White House, with a sense of professionalism that has often been lacking from the administration.

"Grand jury matters are typically secret. The White House favors anything that accelerates the conclusion of his work fairly ... The White House is committed to fully cooperating with Mr. Mueller," Cobb said.

Republican strategist Alice Stewart said on AC360 that the approach from Trump's lawyers was the correct one.

"I was encouraged by the president's attorney saying 'we will fully cooperate' ... which I think is a far cry and a welcome direction from calling this a witch hunt," she said.

One White House source told CNN's Gloria Borger that the President's lawyers were "highly content" to hear about the grand jury, adding that the move was "not causing any anxiety" among the legal team.

Such a cool response is consistent with the team's line that Trump not only has nothing to hide, but wants to get the entire case behind him as soon as possible. And it may not account for rising personal angst that members of Trump's political team may feel at the prospect of being drawn into protracted and costly legal proceedings.

Legal observers agreed that the arrival of a grand jury itself did not necessarily mean Mueller believed that he had found fruitful ground for his investigation.

"It is the end of the beginning," said CNN's Senior Legal Analyst Jeffrey Toobin on CNN's "Erin Burnett Out Front."

Another CNN legal commentator, former Watergate prosecutor Richard Ben-Veniste, said, "It is not at all surprising that we have reached a point involving a grand jury."

But equally, it was clearly a significant step.

Former CIA analyst and FBI official Phil Mudd said he didn't buy the White House message that no one was rattled.

"The White House is obviously going to be anxious about this. I don't believe a word they are saying. I think this suggests Robert Mueller has some smoke," said Mudd, a senior CNN analyst.

In West Virginia, Trump concluded a five-minute riff on Russia with a caustic jab at Democrats who allege that he had an unfair leg up -- from a US enemy -- to defeat Clinton in last year's presidential election.

"Try winning at the voter booth. Not going to be easy, but that is the way you are supposed to do it."