On his way into the courtroom for the day's proceedings, Trump once again alleged that the trial constitutes election interference, claiming that the proceedings are unfairly keeping him off the campaign trail.

"Everybody knows that I'm here instead of being able to be in Pennsylvania and Georgia and lots of other places campaigning, and it's very unfair," he told reporters.

"It's a very, very sad day in America," he said. "I can tell you that."

The former president is seated at the defense table between his lawyers Todd Blanche and Emil Bove.

-Mike Pappano

The proceedings are underway in former President Donald Trump's hush money trial. Trump and Manhattan District Attorney Alvin Bragg are both in the courtroom.

Three prosecutors -- Joshua Steinglass, Matthew Colangelo, and Susan Hoffinger -- are seated at the counsel table.

Bragg is seated in the front row of the gallery with approximately a dozen lawyers and staff from his office.

The first witness prosecutors with the Manhattan DA's office plan to call is former National Enquirer publisher David Pecker, according to two sources familiar with the matter.

ABC News previously reported that prosecutors planned to call Pecker as a witness, but sources now say he's expected to be the first witness to take the stand.

Pecker served as the longtime chief executive of American Media Inc., which published the National Enquirer.

Shortly after Trump announced his 2016 presidential campaign, Pecker met with Trump and agreed to act as the "eyes and ears" of the campaign by looking out for and killing negative stories about Trump, according to the Manhattan DA.

As part of the arrangement, Pecker allegedly directed a deal to pay $30,000 to a former Trump Tower doorman regarding the false allegation that Trump allegedly fathered a child out of wedlock, prosecutors say. Then-Trump attorney Michael Cohen allegedly insisted that the deal stay in place even after AMI discovered the allegation was false, and AMI paid the doorman, according to the Manhattan DA.

-Katherine Faulders

After a week-long selection process, the jurors in Donald Trump's New York hush money case are scheduled to hear opening statements this morning in the first criminal trial of a former U.S. president.

To prove their case, lawyers for Manhattan District Attorney Alvin Bragg need to convince twelve jurors beyond a reasonable doubt that Trump repeatedly falsified records to unlawfully influence the 2016 presidential election.

"This case has nothing to do with your personal politics or your feelings about a particular political issue," prosecutor Joshua Steinglass told prospective jurors on Thursday. "It's not a referendum on the Trump presidency, a popularity contest, or any indication of who you plan to vote for this fall. This case is about whether this man broke the law."

Trump's lawyers are expected to focus their efforts on going after the credibility of prosecution witnesses, suggesting the case itself is politically motivated and arguing that the former president never intended to commit a crime.

In June of 2016, as the National Enquirer evaluated the merits of Karen McDougal's claim of a year-long affair with Trump, Trump's attorney Michael Cohen instructed Pecker to purchase her story -- and suggested that Trump would compensate the company for the cost, according to Pecker.

Pecker recalled from the stand a conversation he had with Cohen, in which Cohen told him, "You should go ahead and buy this story."

"So I said to him … 'Who's going to pay for it?'' Pecker testified, saying Cohen replied, "'Don't worry, I'm your friend, the boss will take care of it.'"

Pecker said he interpreted that to mean that if the National Enquirer purchased the story, Trump or the Trump Organization would reimburse him.

Picking up on his testimony from Tuesday, Pecker said that when he spoke with Trump about McDougal's story, he recalled that Trump called McDougal "a nice girl" and asked Pecker what he should do about it.

"I think you should buy this story and take it off the market," Pecker said, explaining that he "believed the story was true. I think that it would be embarrassing to himself and also to his campaign."

During her negotiations with the National Enquirer, McDougal represented that "she didn't want to be the next Monica Lewinsky," Pecker said.