Julian Zelizer is a history and public affairs professor at Princeton University, editor of " The Presidency of Barack Obama: A First Historical Assessment " and co-host of the "Politics & Polls" podcast. Follow him on Twitter: @julianzelizer . The opinions expressed in this commentary are those of the author. View more opinion articles on CNN.

(CNN) The nation has been watching an epic battle between fact and fiction for more than a year. This week, with the major legal developments regarding Paul Manafort and Michael Cohen (President Donald Trump's former campaign manager and fixer, respectively) the power of facts dealt a serious blow to Trump's endless cries of "witch hunt."

With the convictions of Trump's associates starting to pile up and a Fox News poll showing an increase in approval of Special Counsel Robert Mueller's Russia investigation this month, it seems that the tide is turning against the President. For anyone who has given up on the belief that fact will win out in a political world with so much fiction, the reverberations from this week should provide a modicum of hope.

Despite widespread hope that it will be wrapped up by midterm elections, the Russia investigation will heat up even more, and so will the battle between Trump and Mueller. The dichotomy of the two men's modi operandi couldn't be starker: Here is Trump using his bully pulpit to spin and twist the facts and create an alternative narrative. And here is Robert Mueller, the tough and quiet prosecutor who depends on the truth, laid bare through indictments and convictions, to speak for itself.

Although Mueller does not have the same massive platform as the President, or a passionate and loyal political base that will back him in any situation, he does have the capacity to shape public opinion through the report he will ultimately produce.

We don't yet know what Trump's relationship was to the Russian attack on the 2016 election, or how far he went to obstruct the Russia investigation -- and Democrats should pause before making any assumptions. But we are already seeing a pretty devastating portrait of the people the President has surrounded himself with. And Cohen's statement in the courtroom that he acted "in coordination and at the direction of a candidate for federal office," appears to indicate that Trump was willing to go beyond the boundaries of the law to win the presidency. Trump has denied wrongdoing.

As the Russia investigation enters its next phase and converges with midterm season, the country's immediate future will hinge on how the public interprets any revelations made public. Based on his own record, President Trump will work tirelessly to manipulate each part of this story to promote a narrative that vindicates him and impugns his critics.

Trump's statements indicate he is willing to bring down entire institutions to protect himself. His critics should not take the threat that he poses lightly; they should realize that in our current political world, the truth often doesn't win out. The President has already shown his capacity to shape national conversations with smears that have no basis in fact. He delegitimizes people, organizations and institutions by throwing political mud at the wall to see what will stick. Much of it does, and his base remains strong.

Nonetheless, President Trump and his ardent supporters should not be so sure this will work every time. If Mueller's report is damning to the President, it will offer the biggest counterpunch to the Trumpian world of spin. The legal damage in this investigation is already starting to mount, and --- even if Mueller's report does not come out before November -- Republicans will still very likely be the first to pay the price in the midterm elections.

If Democrats gain control of Congress in November and Mueller's report suggests that the President has committed high crimes and misdemeanors, the findings must be powerful enough to sway Democrats to move forward with impeachment and convince enough Senate Republicans to concur. If Republicans retain a slim majority in Congress, the report would somehow have to shake Republicans from their partisan loyalty and convince them to do something to constrain Trump.

Even if the President can survive a bad report from Mueller, it remains to be seen whether his capacity to sell his fans on the world he imagines will be enough to win him reelection in 2020.

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Some people have recently been wearing T-shirts that read "It's Mueller Time." Well, the verdict will be out soon and we'll see then how many more people will be sporting that phrase.

Soon we'll know how much our political world has been broken and whether there is any hope for regaining normality -- and returning to a nation where facts actually matter.