The prosecution's star witness, former Trump attorney Michael Cohen, called today's verdict "an important day for accountability and the rule of law."

"While it has been a difficult journey for me and my family, the truth always matters," he said.

Two senior Trump advisers who ABC News spoke with were extremely angry after the verdict.

Both said they were not surprised by the jury’s decision. One said, "The fix was always in," and the other added, "Not surprised -- it’s New York."

Donald Trump Jr., reacting to his father's guilty verdict, said, "The Democrats have succeeded in their yearslong attempt to turn America into a third-world s---hole. Nov. 5 is our last chance to save it."

The guilty verdict shows "no one is above the law," a representative for President Joe Biden's campaign said, adding, "But today's verdict does not change the fact that the American people face a simple reality. There is still only one way to keep Donald Trump out of the Oval Office: at the ballot box."

"Convicted felon or not, Trump will be the Republican nominee for president," Michael Tyler, communications director for the Biden-Harris campaign, said in a statement.

"A second Trump term means chaos, ripping away Americans' freedoms and fomenting political violence -- and the American people will reject it this November," Tyler said.

The White House offered a very brief comment, with a White House Counsel’s Office spokesperson saying, "We respect the rule of law, and have no additional comment."

Among the congressional response, Speaker of the House Mike Johnson, who traveled to Manhattan days ago to support Trump at the trial, said in a statement, "Today is a shameful day in American history. Democrats cheered as they convicted the leader of the opposing party on ridiculous charges, predicated on the testimony of a disbarred, convicted felon."

"President Trump will rightfully appeal this absurd verdict -- and he WILL WIN!" Johnson said.

Former President Donald Trump's campaign is already fundraising off of the guilty verdicts in his hush money trial, telling his supporters he has been convicted in a "rigged" trial.

"I was just convicted in a RIGGED political Witch Hunt trial: I DID NOTHING WRONG!" a fundraising email said. "They’ve raided my home, arrested me, took my mugshot, AND NOW THEY’VE JUST CONVICTED ME!" the email continues.

The email links to a fundraising page, in which Trump told his supporters, "I'm a political prisoner!"

The jury heard an exchange between David Pecker and defense attorney Emil Bove where Bove highlighted that Pecker originally thought the Trump Tower meeting took place in the first week of August 2015. Pecker testified that the meeting actually happened in the middle of August.

Bove used the moment as an opportunity to highlight "gaps" in Pecker's memory and emphasize how long ago the meeting took place.

Q: And you changed your testimony here; right?

A: Yes, when I discovered that it was in the middle -- that it was the middle of August.

Q: And when you say that you "discovered," what you mean is that somebody told you that, notwithstanding what you testified about in the Grand Jury, President Trump was actually not in New York City during the first week of August; correct?

A: I -- I don't recall anyone telling me about that, that Mr. Trump was away in the first week of August.

Q: And then you changed your testimony, this week, on that issue; right?

A: Yes, that's correct.

Q: Why did you change your testimony?
A: I thought that -- I didn't know the exact date. I thought -- I know it was in the first half of August, so I thought it was the middle of August, that's what I recollected. That's why I corrected my -- the dates, yes.

A: I didn't believe that the exact date was --

Q: I understand. And I don't mean to put you on the spot. What I'm getting at, though, is that these things happened a long time ago; right?

A: Yes.

Q: And even when you're doing your best, and I'm sure you are right now, it's hard to remember exactly what happened when; right?

A: Yes.

Q: And when you are remembering about conversations that you had, it's hard to remember what people said almost ten years ago; correct?

A: You -- Ahhhh, yes.

Q: And so there are some instances where your mind sort of fills in gaps; right?

A: To the best of my knowledge.

Q: And you do your best to explain what happened in a way that makes sense; correct?

A: To what I remember.

Q: Yeah, to what you remember. And you fill in some details to keep things in sequence; right, and to make them sound logical?

A: I try to make them -- to what I remember. And to be truthful.

Q: I understand. But there are some gaps; correct?

A: Yes.