The impeachment trial of Vice President Sara Duterte of the Philippines is set to begin on Monday, in a case that has highlighted a bitter fight between the country’s two most powerful political dynasties.

Lawmakers have accused Ms. Duterte, the daughter of the Philippines’ previous president, of embezzlement and of betraying the public’s trust by threatening to assassinate President Ferdinand Marcos Jr., who is also a political scion. The stunning falling-out came just four years after the Marcoses and the Dutertes joined forces in 2022.

Ms. Duterte, who became vice president in 2022 after joining Mr. Marcos’s ticket, has denied the allegations, contending that they were meant to derail her political ambitions. She has announced plans to run for president in 2028, following in the footsteps of her father, the former president Rodrigo Duterte, who is in prison in The Hague, awaiting trial on charges of crimes against humanity for a brutal drug war that he set off.

Last month, Ms. Duterte’s legal team called the case “constitutionally infirm, procedurally defective and substantively deficient.”

In the Philippines, as in the United States, the Senate tries and decides whether to convict an official who is impeached by the House of Representatives. Here is what to know about the proceedings.

Ms. Duterte has been impeached twice.

An overwhelming majority of the House voted to impeach Ms. Duterte in May. Lawmakers raised concerns about wealth they said she had amassed as mayor of Davao beginning in 2019, and alleged that she had misused funds as vice president and during her tenure as education secretary from 2022 to 2024. She also faced complaints for saying she had planned to kill Mr. Marcos.

She was previously impeached last year on the same charges, shortly after she said she had arranged for someone to assassinate Mr. Marcos if she were to be killed. The Supreme Court found those proceedings unconstitutional, and the Senate voted to archive the impeachment.

Two-thirds of the 24-member Senate is needed to convict Ms. Duterte. If convicted, she will be removed from office and barred from running for future office.

Ms. Duterte’s allies in the Senate recently lost control of the majority after briefly taking over in May, a shift that could make conviction more likely. Her father’s former police chief, Senator Ronald dela Rosa, who is wanted by the International Criminal Court over accusations about his role in the drug war, briefly emerged from hiding to help stage the takeover. But he later fled after causing chaos in the Senate that ended in gunfire.

The trial is the culmination of a falling-out between two powerful political clans.

In 2022, Ms. Duterte agreed to run as Mr. Marcos’s vice president, and they won in a landslide. The president and vice president are separately elected in the Philippines, a mechanism meant as a political check and balance.

But the alliance quickly crumbled as the House began examining Ms. Duterte’s budget. Things came to a head with her father’s arrest last year.

The elder Duterte ran the country from 2016 to 2022, during which his brutal war on drugs killed thousands. Mr. Marcos had initially vowed to protect him from criminal prosecution, but then handed him over to the I.C.C. last year. Mr. Duterte has called the allegations against him a farce engineered by his enemies.

Mr. Marcos has said he is not involved in Ms. Duterte’s impeachment proceedings.

The proceedings have deepened a political divide in the Philippines.

Analysts say the impeachment process has deepened the divide in a country where a handful of prominent families control politics and corruption is rampant.

Edmund Tayao, a political analyst in Manila, said Congress had followed the impeachment process as dictated by the Philippine constitution.

But he expressed concern that Duterte supporters, who massed outside the Senate in May in support of Mr. dela Rosa, might threaten the integrity of the trial.

Chester Cabalza, founder of the International Development and Security Cooperation, a Manila-based research institute, said that what was currently playing out was “about a calculated power struggle between two leading and competing dynasties.”

For supporters of the Dutertes, he said, the trial is a “selective political vendetta” aimed at crippling the family ahead of elections. For their critics, it is about accountability.

Mr. Tayao said he doubted there would be a conviction. Still, if the evidence were laid out for the public to scrutinize, he said, “this could be the end of the Duterte political name.”

The trial is expected to be long and contentious.

Leila De Lima, a member of the House who is on the prosecutorial team, said that she expected the trial to be “tedious and lengthy,” and that prosecutors were expecting “sustained online attacks.”

Ms. De Lima, who spent more than six years in jail on charges filed by Mr. Duterte’s government before being cleared and freed, acknowledged that an impeachment case was “political in nature” but said the evidence in this case was strong.

“You cannot say it is political persecution if the constitutional and legal requirements for an impeachment complaint are being followed,” she said.