Washington (CNN) No wonder the President is lashing out.

Donald Trump waited 10 long months for the vindication of his first legacy-boosting win on Capitol Hill -- the Senate vote on tax reform. But his triumph, when it came, was tainted by his worst moment as President -- the plea deal ensnaring fired national security adviser Michael Flynn that epitomizes special counsel Robert Mueller's relentless march closer to the Oval Office.

In recent days, the strands that define this political era of incredulity and turmoil, including the tax bill, the Russia investigation and the escalating threat of war with North Korea, have come together at a frenetic moment that will shape the environment ahead of the midterm elections next November, but also the 45th President's place in history.

Republican efforts to finally get the tax bill to Trump's desk by the end of the year coincide with an ominous turn of the Mueller probe after Flynn became the fourth Trump associate to be charged, raising the possibility he could testify against the President, and his son-in-law, Jared Kushner, and son Donald Trump Jr.

One of the key questions following Mueller's strike against Flynn on Friday was how Trump would react. Predictably, the President exploded on Twitter , denying wrongdoing, slamming his own FBI and casting doubt on whether justice would be served by Mueller's investigation.

"I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide!" he tweeted Saturday morning. In another tweet, he said the FBI's reputation is in "tatters."

I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide! — Donald J. Trump (@realDonaldTrump) December 2, 2017

After years of Comey, with the phony and dishonest Clinton investigation (and more), running the FBI, its reputation is in Tatters - worst in History! But fear not, we will bring it back to greatness. — Donald J. Trump (@realDonaldTrump) December 3, 2017

And it all backfired, adding to the impression that Trump is often his own worst political enemy and suggesting that Mueller is sowing panic in the White House and undercutting the notion that the President's incessant tweeting is the secret of his success.

Worsening fallout

JUST WATCHED Trump's lawyer says he wrote Flynn tweet Replay More Videos ... MUST WATCH Trump's lawyer says he wrote Flynn tweet 01:48

Trump worsened the fallout from the Flynn plea with a tweet from his account on Saturday that said he fired his former close aide earlier this year because he had lied to Vice President Mike Pence and the FBI over conversations with Russian officials. The comment set off a political firestorm and raised the question of whether he had effectively and inadvertently admitted to obstructing justice.

If Trump knew that Flynn had lied to the FBI when he asked James Comey in February, by the former FBI director's own account, to go easy on his fired national security adviser, he could be seen as advocating a cover-up of a crime.

Trump lawyer John Dowd eventually insisted that he, and not Trump, had written the tweet.

CNN legal analyst Michael Zeldin said Sunday that Dowd would have tweeted in the first place only if Trump had asked him to do so, or he had made a "terrible mistake."

"It did create a huge mess for the President as a consequence of it," said Zeldin, who said he did not believe it was possible that Trump knew Flynn lied to the FBI when he fired him.

The episode hinted at the extreme pressure and even panic being generated inside the West Wing with each stride that Mueller takes, a state of mind apparently also reflected in Trump's wild weekend tweets.

Another tweet also appeared to dig Trump deeper into the legal and political mire.

"I never asked Comey to stop investigating Flynn. Just more Fake News covering another Comey lie!" Trump tweeted on Sunday.

I never asked Comey to stop investigating Flynn. Just more Fake News covering another Comey lie! — Donald J. Trump (@realDonaldTrump) December 3, 2017

On its own, the tweet does not incriminate Trump, but it exemplifies the legal peril in which he now finds himself.

That's because if he repeated that statement under oath to Mueller's team, it would set up a direct clash with the sworn public testimony of Comey, who said, with the support of contemporaneous notes, that Trump did indeed ask him to end the Flynn investigation.

If the President repudiates his own position, he would be effectively admitting trying to interfere in a federal investigation.

Either scenario could pose grave legal and political risks to Trump and his presidency. And both raise a fateful question: Why was the President so keen to thwart the Flynn investigation, and what does the former national security adviser know about alleged election collusion with Russia that he is now compelled to tell Mueller?

Comey took to Twitter himself Sunday evening to fire back at Trump, recycling a quote from his congressional testimony in June.

"I want the American people to know this truth: The FBI is honest. The FBI is strong. And the FBI is, and always will be, independent."

Me (June 8, 2017) pic.twitter.com/OZ1ZiBrMNL — James Comey (@Comey) December 3, 2017

"I want the American people to know this truth: The FBI is honest. The FBI is strong. And the FBI is, and always will be, independent," Comey tweeted.

California Sen. Dianne Feinstein exemplified the darkening storm around the White House in an appearance on NBC's "Meet the Press."

"What we're beginning to see is the putting together of a case of obstruction of justice," said Feinstein, the top Democrat on the Senate Judiciary Committee, which is conducting its own Russia investigation.

Tax reform win

JUST WATCHED Winners and losers of the Senate tax bill Replay More Videos ... MUST WATCH Winners and losers of the Senate tax bill 02:37

The weekend of deepening intrigue over the Mueller investigation robbed the President of a chance to get full political value for the Senate's vote on tax reform.

"We are one step closer to delivering MASSIVE tax cuts for working families across America," the President tweeted on Saturday morning, trying his best to mark the most momentous legislative moment of his presidency.

We are one step closer to delivering MASSIVE tax cuts for working families across America. Special thanks to @SenateMajLdr Mitch McConnell and Chairman @SenOrrinHatch for shepherding our bill through the Senate. Look forward to signing a final bill before Christmas! pic.twitter.com/gmWTny3SfS — Donald J. Trump (@realDonaldTrump) December 2, 2017

While the tax reform measure is highly controversial, saw long-time fiscal conservatives repudiate their past as deficit hawks and is branded by Democrats as a massive giveaway to the rich at the expense of the middle class, it will rate as a significant victory for Republicans when the House and Senate versions are combined and sent for Trump's signature.

The bill is the most far-reaching reform of the tax code since the Reagan era. It finally offers validation for the GOP's monopoly on Washington power. GOP candidates at last have a win to sell to midterm voters. It is a measure that will stand with Trump's name in history and also revives the reputation of Majority Leader Mitch McConnell, who saw his aura as a master of the Senate dulled by the failure to pass an Obamacare repeal bill.

When Trump signs the measure, as now seems likely, his critics will no longer be able to mock him for lacking a single big legislative win during his first year in office, the time when a president's power is at its apex.

However, it is too soon to assess the enduring political impact of the tax bill.

Republicans believe that provisions including a 15% cut in the corporate tax rate will ignite a golden economic era, previewed by the impressive rate of 3.3 % growth in the gross domestic product in the third quarter, which represents one of the bright spots of the Trump presidency.

JUST WATCHED Scott: tax analysis 'inconsistent with reality' Replay More Videos ... MUST WATCH Scott: tax analysis 'inconsistent with reality' 02:49

"We are in a global competition. We must win that competition, which means that our tax code must be competitive with the rest of the world," South Carolina Republican Sen. Tim Scott told CNN's Jake Tapper on "State of the Union."

"When that happens, American companies will churn out more profits, more revenues to the government, and we will be able to deal with our national debt," he said.

If Scott is correct, the stock market will extend its bull run, more Americans will be working and companies will be opening new factories, providing a favorable economic environment for Republicans as they head into midterm elections.

Those Republican voters souring on Trump's volatile behavior may give him a pass in his re-election bid if he is delivering roaring prosperity.

Key moment for Democrats

JUST WATCHED Granholm: GOP tax bill an 'outrage' Replay More Videos ... MUST WATCH Granholm: GOP tax bill an 'outrage' 06:56

But this is a key moment for Democrats as well.

Top party officials sense a political opening, believing the measure will bloat the deficit by more than $1 trillion and cause corporations to use their windfall for share buybacks and dividends rather than invest in their own operations to create more jobs.

They accuse Trump of turning his back on the white working class on which he built his political base, hoping to stifle the Republican renaissance in the Midwest. They also predict that the bill will cause the GOP to slash the beloved social programs that Trump vowed in 2016 to protect.

"Mr. President, you told the American people time and time again you were not going to cut Social Security, Medicare and Medicaid," Vermont Sen. Bernie Sanders, an independent who vied for the 2016 Democratic presidential nomination, said Sunday at a rally in Reading, Pennsylvania.

"Today, get on the phone. Tell Paul Ryan, tell Mitch McConnell that you will veto any bill that cuts Social Security, that cuts Medicare, that cuts Medicaid," Sanders said.

As domestic politics and Mueller's threat to Trump dominated a weekend of cascading political developments, there was a new twist to the third dominant issue demanding the administration's attention -- North Korea.

The current national security adviser, H.R. McMaster, warned that the prospect of a conflict that could be one of the most devastating in decades and even go nuclear was "increasing every day."