When the impeachment inquiry opened in September, it centered on a single question: Did President Donald Trump block U.S. military aid to muscle Ukraine into investigating Joe Biden and others, and risk national security to boost his reelection campaign?
The evidence is steadily mounting that he did.
Now, the scandal is expanding.
It has intersected with the federal prosecution of two Soviet-born associates of Trump's buccaneering personal lawyer, Rudy Giuliani, for allegedly funneling Russian money into a U.S. political campaign.
It has revealed further Russian influence in our politics, the exploitation of Moscow-style disinformation to take down a respected U.S. ambassador and smear a potential Democratic rival to Trump.
Most important, it has begun to feature a shadowy figure who always seems to be just offstage: Russian President Vladimir Putin.
Russia was repeatedly invoked on Friday by Marie Yovanovitch, the former U.S. ambassador to Ukraine, as she recounted Giuliani's successful campaign to get her ousted from Kyiv - apparently because her anti-corruption efforts there got in the way of his clients' business.
"How is it that foreign corrupt interests could manipulate our government?" she asked during a day of riveting testimony before the House Intelligence Committee. "Which country's interests are served when the very corrupt behavior we have been criticizing is allowed to prevail?"
She answered her own question.
"Such conduct undermines the U.S. ... and widens the playing field for autocrats like President Putin," she said.
This week, Putin will move onto center stage when the House committee questions Fiona Hill, a former CIA analyst who worked inside the Trump White House for more than two years.
Hill is a leading authority on Putin. She was hired by Trump's first national security advisor, Michael Flynn, and kept on by Flynn's successors, H.R. McMaster and John Bolton. All three quit or were pushed out.
But Hill remained the White House's top Putinologist until she resigned in July. She's not a "never Trumper."
And what she has to say is chilling.
"Corruption is our Achilles' heel," she told the House committee in her closed-door deposition last month. "Corruption is the way President Putin and other nefarious actors, be they from China, Iran or North Korea, access our system."
Putin has been trying to compromise influential Americans since the 1970s, when he began his KGB career as a case officer in Leningrad, she said.
She did not charge that Putin had succeeded in compromising Trump. But she said Trump's history as a businessman who spent years trying to land a real estate project in Moscow put him in Putin's sights long ago.
"It's what Putin did," she said. "They went after American businessmen and set up sting operations."
We know that Russian intelligence escalated its operations on U.S. soil during the 2016 election. But Hill says Putin not only targeted Trump, but "was targeting all of the other campaigns as well."
"Compromising material was being collected on a whole range of individuals," she said. "It was most definitely being collected on (Hillary) Clinton."
Her larger point is clear. We have failed to adequately protect our political system by using voting systems that are vulnerable to hacking, and by allowing foreign disinformation to corrupt our social media and political debates.
"By not cleaning up our act, (we) have given them the doors which they can walk through and mess up our system," she told the House committee. "The Russians can't exploit corruption if there's not corruption."
This will be an unwelcome message for Trump, who says Ukraine interfered in the 2016 election to help Clinton. No evidence of that hallucinatory claim has emerged.
Instead, the U.S. intelligence community and a special counsel investigation concluded that Putin authorized the hacking of Democratic Party computers and conducted a massive disinformation operation on social media, all to help Trump.
Trump has dismissed the overwhelming evidence of Russian meddling. Instead, he has embraced the bizarre alternative narrative that someone in Ukraine is hiding a computer server containing all the evidence.
That, says Hill, is "a conspiracy theory."
Even worse, it's a conspiracy theory that serves the interests of Putin, who wants to drive a wedge between the U.S. and Ukraine, a U.S. ally that is fighting a Russian-backed insurgency.
"Russia can take advantage of this," Hill said. "Putin's whole schtick since 2016 has been, 'We didn't do it ... Pin it on whoever.' "
Ever since his election, Trump has insisted that he won the White House fair and square and that charges of foreign meddling on his behalf were invented by his enemies.
His actions toward Russia have been contradictory and baffling. Trump has been indulgent, even deferential toward Putin, while official U.S. policy considers Russia one of America's main adversaries.
No one has determined whether the president's fawning relationship with Putin is driven by his desire to shake off the charge that he was put in office with the Kremlin's help, or something more sinister.
But if the question is who has benefited from Trump's actions, in Ukraine and elsewhere, the answer has been depressingly constant: Vladimir Putin.
Doyle McManus wrote this for the Los Angeles Times.