In the official record, the case is known as the People of the State of New York v. Donald J. Trump, and, for now, the people have the stronger hand: They have insider witnesses, a favorable jury pool and a lurid set of facts about a presidential candidate, a payoff and a porn star.

On Monday, the prosecutors will formally introduce the case to 12 all-important jurors, embarking on the first prosecution of an American president. The trial, which could brand Mr. Trump a felon as he mounts another White House run, will reverberate throughout the nation and test the durability of the justice system that Mr. Trump is attacking in a way that no other defendant would be allowed to do.

Though the district attorney, Alvin L. Bragg, has assembled a mountain of evidence, a conviction is hardly assured. Over the next six weeks, Mr. Trump’s lawyers will seize on three apparent weak points: a key witness’s credibility, a president’s culpability and the case’s legal complexity.

Daniel J. Horwitz, a veteran defense lawyer who previously worked in the Manhattan district attorney’s office prosecuting white-collar cases, said prosecutors can be expected to corroborate Mr. Cohen’s story wherever possible.

“The prosecution has layers upon layers of evidence to back up what Michael Cohen says,” Mr. Horwitz said.

But in previewing the case for prospective jurors last week, Manhattan prosecutors emphasized neither the payoff that secured Ms. Daniels’s silence, nor the sex scandal that was buried in the process. One prosecutor, Joshua Steinglass, instead distilled the trial’s stakes to a fundamental question: “This case is about the rule of law and whether or not Donald Trump broke it.”

Mr. Steinglass’s boss, Mr. Bragg, has offered a loftier interpretation, casting Mr. Trump’s actions as election interference. Although Mr. Trump’s lawyers might claim he was merely trying to hide embarrassing stories from his family, Mr. Bragg says Mr. Trump orchestrated a scheme to conceal simmering sex scandals from voters as they headed to the polls in 2016. All told, his allies struck three hush-money deals, paying off people who had stories to tell — stories that could have derailed Mr. Trump’s candidacy.

Mr. Bragg’s prosecutors will seek to turn that 2016 campaign strategy against him: The tactics that helped propel Mr. Trump to victory will be admitted as evidence and reconsidered far beyond the courtroom. Aides and friends who lied on Mr. Trump’s behalf will take the witness stand to testify against him.

They include: David Pecker, the tabloid publisher who bought and buried damaging stories about Mr. Trump; Hope Hicks, a spokeswoman who tried to spin reporters; and Mr. Cohen, the fixer who paid Ms. Daniels. Mr. Pecker, who ran the company that owned The National Enquirer, is set to go first, and is expected to recount for the jury several conversations with Mr. Trump about the hush money, according to a person familiar with the plan.

Mr. Trump faces 34 felony counts, and up to four years behind bars, but more than just his freedom is at stake. If convicted, he might lose the right to vote, including to cast a ballot for himself. If he were to win back the White House, he would be the first convicted criminal to serve as commander in chief. And the question of how he might serve a prison sentence, should it come to that if he does not receive probation, could throw the country into turmoil.

America has grown accustomed to seeing Mr. Trump smash through its customs and is now witnessing a phenomenon that is a first in the 248 years of its history. Presidents have been impeached, driven from office and rejected at the polls. Mr. Trump is about to be the first to have his fate decided not just by voters, but by 12 citizens in a jury box.

And they all hail from Manhattan, the borough that made Mr. Trump famous, and where he is now deeply unpopular. A favorable jury pool, legal experts say, has given Mr. Bragg a leg up at the trial.

Yet the jury, which was made final on Friday and includes six alternates, is no rubber stamp: It includes at least two people who have expressed some affection for the former president, and it takes only one skeptical member to force a mistrial, an outcome that Mr. Trump would celebrate as a win.

The stakes are high for Mr. Bragg as well. He is betting his career and his legacy on a prosecution he inherited, rejected and then transformed.

When he took office in 2022, he declined to bring a financial fraud case against Mr. Trump that his predecessor had prepared, prompting an uproar when two prosecutors resigned in protest.

But Mr. Bragg continued to investigate and soon revisited the hush-money deal — an episode that had become known internally as “the zombie case,” because it kept coming back to life. Little more than a year after taking office, Mr. Bragg indicted the former president.

Three other indictments followed in three other cities, but with those cases mired in delay, Mr. Bragg’s trial may now be the only one that Mr. Trump will face before Election Day.

The Manhattan case comprises the three hush-money deals: with Ms. Daniels, with a former Playboy model and with a onetime doorman who told a tale of Mr. Trump fathering a child out of wedlock.

Then there was Ms. Daniels, who was interested in selling her story of a sexual encounter with Mr. Trump. Mr. Pecker drew the line there: Her price was too high.

Instead, he and a top editor alerted Mr. Cohen, who soon paid Ms. Daniels $130,000 not to tell her story about a sexual encounter with Mr. Trump a decade earlier.

Mr. Cohen has said he acted at Mr. Trump’s direction, but the former president is not charged over the payment itself. Instead, he stands accused of covering up the transaction by disguising reimbursements to Mr. Cohen.

In internal records, Mr. Trump’s company marked those payments as legal expenses, citing a retainer agreement. Yet no such expenses existed, prosecutors say, and the retainer agreement was fictional.

Mr. Trump is accused of engineering — or, at least, approving — the coverup. His company, prosecutors argue, produced 34 false records that underpin the counts against him: 11 checks, 11 monthly invoices Mr. Cohen submitted and 12 entries in the general ledger for Mr. Trump’s trust.

Mr. Trump signed several of the checks in the White House, as prosecutors will surely point out at the trial.

But directly linking Mr. Trump to the plot to falsify those records is another matter altogether.

His lawyers will be likely to argue that he was oblivious, and that Mr. Cohen handled the specifics. Mr. Cohen hashed out the reimbursement plan with Mr. Trump’s chief financial officer, Allen H. Weisselberg, who is serving jail time for perjury and will not testify, records show.

The lack of a firsthand witness to confirm Mr. Cohen’s account is a potential flaw in the case, but it may not be fatal. Prosecutors plan to introduce a document containing Mr. Weisselberg’s handwritten notes about the reimbursements — a key piece of evidence demonstrating that Mr. Cohen did not act alone.

And under the law, the prosecutors need not prove that Mr. Trump personally falsified the records. Already during the trial’s first week, Mr. Steinglass laid the groundwork with a simple analogy: He asked prospective jurors whether they could accept that, if a husband hired a hit man to murder his wife, the husband was just as guilty as the man who pulled the trigger.

“Can you all follow the same kind of logic in this case?” Mr. Steinglass asked the prospective jurors. Many said they could.

Mr. Cohen is expected to offer the closest thing this case has to a smoking gun: He is likely to say that, in early 2017, he and Mr. Trump discussed the repayment scheme in the Oval Office.

If Mr. Trump testifies in his own defense, that could pit Mr. Cohen’s word against Mr. Trump’s — a he-said, he-said story, with two questionable narrators.

Whether or not Mr. Trump takes the stand, the trial could become a referendum on Mr. Cohen’s credibility, with the verdict possibly hinging on a convincing performance.

In 2018, Mr. Cohen pleaded guilty to a variety of federal crimes, admitting to participating in the hush-money deals with Ms. Daniels and Ms. McDougal and lying to Congress about plans for a Trump business deal in Russia. Mr. Trump’s lawyers will seek to emphasize Mr. Cohen’s checkered past at every turn.

And, on cross-examination, Mr. Trump’s lawyers are likely to portray Mr. Cohen as a serial liar with a grudge against his former boss.

Susan Necheles, one of Mr. Trump’s lawyers, began that campaign during jury selection. She referenced Mr. Cohen’s 2022 book “Revenge,” questioning the credibility of “someone who says that they want revenge against President Trump.”

Yet the prosecution is expected to note that Mr. Cohen told many of his lies for Mr. Trump. And prosecutors will offer evidence corroborating the broad strokes of Mr. Cohen’s story, which could persuade jurors when they are weighing his testimony about the crucial Oval Office meeting.

Mr. Trump’s White House executive assistant, Madeleine Westerhout, who has been identified as a potential witness, could confirm that Mr. Cohen did indeed meet with Mr. Trump, even if she cannot confirm what they discussed. Mr. Pecker can support at least some of Mr. Cohen’s testimony about Mr. Trump’s involvement in the hush-money deals. And a recording Mr. Cohen made of a call he had with Mr. Trump will capture the former president discussing the deal with Ms. McDougal.

“The prosecution’s argument is that you can trust Michael Cohen beyond a reasonable doubt as to their isolated conversation,” said Mr. Horwitz, the former prosecutor. He called the approach “Prosecuting 101.”

William K. Rashbaum, Maggie Haberman, Jonathan Swan and Michael Rothfeld contributed reporting.