Paul Manafort is well and truly screwed and we might be, too. The FBI had such damning evidence against him that even during the 2016 election, a judge signed off on a warrant to wiretap Manafort's communications and that surveillance continued after Trump was sworn in as president:
The FBI resumed surveillance under a new FISA warrant at some point last year and continued to monitor him into 2017, CNN said. The second warrant was obtained as part of the FBI’s investigation into ties between Trump campaign associates and Russian operatives, it said.
FISA warrants require the approval of top FBI and Justice Department officials, and law enforcement has to demonstrate to the court that there is reason to believe that the subject of the investigation may be acting as an agent of a foreign power.
I'm not an expert on FISA warrants but it's obvious even to the casual observer that the bar for granting such a warrant would have to be astronomically high. Regardless, the FBI got it anyway and Manafort was already sloppy about security in his various illegal dealings with Russia. One can only imagine what he divulged when he thought he was "safe."
There's a reason John Oliver keeps calling this "Stupid Watergate."
Depending on whose reporting you listen to, the FBI may or may not also have recorded conversations between Manafort and Trump and that's where this potentially gets ugly.
Unlike the Nixon tapes, Trump cannot refuse to turn them over. They're not in his possession and not under his control. He can't tell Attorney General Jeff Sessions to confiscate them because he's recused himself from anything to do with the Russia investigation and Deputy Attorney General Rod Rosenstein only answers to Sessions. This is the same problem Trump has faced for months and the only way around it is to fire Sessions and order Rosenstein to do his dirty work.
When Rosenstein almost certainly refuses (he did, after all, start the investigation in the first place), Trump will have to fire him and keep his own "Saturday Night Massacre" going until he finds someone willing to take over as acting Attorney General that will be willing to order the Director of the FBI Christopher Wray to make the tapes disappear. And if Wray refuses, his will be the shortest tenure as director in history as Trump continues firing people until only sycophants remain. If you'll recall, Trump already thinks the FBI should report directly to him so installing a loyalist as acting director would suit him just fine.
Trump's only other option would be to claim executive privilege and have the courts bury the tapes but if they reveal illegal activity it's unlikely that even Gorsuch would throw himself on that grenade for Trump. He may try this route first but if and when it fails, Trump will not allow the wheels of justice to keep turning unimpeded.
That means the worst case scenario Republicans have been dreading, Trump firing Sessions (and anyone else in his way) and seizing control of the DoJ and FBI, will come to pass. They don't dread it because they particularly care about the rule of law, but because the obstruction of justice would be so blatant and egregious that even Fox News, AM Hate Radio and Breitbart won't be able to spin it (not that they won't try).
Trump will have committed a clearly impeachable offense that we, in fact, have forced a president out of office for once before. And a Republican, at that. It's a lose-lose situation for the GOP.
If they force Trump out, either by impeachment or the threat of impeachment, his white nationalist base will revolt and the 2018 and 2020 elections will see Democratic wins that will threaten the GOP's voter suppression schemes and their long-term viability as a national party.
If they turn a blind eye to Trump's no longer deniable crimes, they face an electoral revolt that still threaten their long-term viability as a national party. That's assuming Trump doesn't go ahead and cancel the elections after people riot in the streets over his lawlessness.
The gamble Republicans made on Trump will have cost them possibly everything, including what tiny shred of their souls they have left. And if they stay in power by backing Trump's power grab, it will be at the cost of everything that makes America a nation of laws, democracy, tradition and decency.
But I guess it will have been worth it to get those tax cuts for billionaires, right?