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 in Donald Trump's criminal trial will return to court this morning for their second day of deliberations in the historic case.

After receiving instructions on the law from the judge yesterday morning, the jurors deliberated the case for four and a half hours and sent back two notes, asking to listen to testimony from two key witnesses in the case and to rehear the judge's instructions on the law.

The jury requested to rehear former National Enquirer David Pecker's testimony about a June 2016 phone call with Trump regarding the tabloid's response to a potential story about former Playboy model Karen McDougal's alleged year-long affair with Trump --- which he has denied --- as well as Pecker's decision about allocating the rights to her story.

Jurors also requested to hear both Pecker and Michael Cohen's testimony about the August 2015 Trump Tower meeting where the plan to catch and kill negative stories originated.

Judge Juan Merchan estimated that the entire readback will take approximately 35 minutes, and he also asked the jury to clarify this morning which portion of the instruction they would like read back.