After the first day of jury selection in Donald J. Trump’s criminal trial saw the dismissal of dozens of potential jurors who said they could not be impartial, the first seven jurors were chosen on Tuesday as the defendant looked on.

The picks came after a morning session in which several more potential jurors said that they could not be unbiased, underscoring the challenges of seating a panel in Manhattan, a profoundly Democratic borough.

Mr. Trump, 77, is charged with falsifying nearly three dozen business records in an attempt to cover up a payment to a porn star, Stormy Daniels, who has said she had a brief sexual encounter with him in 2006.

If convicted, he could face probation or up to four years of prison time. Mr. Trump denies having been involved with Ms. Daniels, and has declared his innocence, calling the charges against him a “witch hunt” conjured by the Manhattan district attorney, Alvin L. Bragg, a Democrat.

Here are five takeaways from Mr. Trump’s second day on trial:

We are moving unexpectedly quickly.

The trial is expected to last about six weeks, according to Juan M. Merchan, who is overseeing it, and court officials had warned that the selection of 12 jurors and several alternates might take two weeks.

But Justice Merchan, an experienced jurist known for his no-nonsense style, has kept things moving fast. Before leaving Tuesday, he swore in another 96 prospective jurors, who will return on Thursday — Wednesday is an off day for the trial — raising the possibility that a full jury will be seated this week.