Hundreds of thousands of people have taken to the streets in Puerto Rico to demand the resignation of the island's embattled governor, Ricardo Rosselló.
It comes a day after Mr Rosselló said he would not step down over a leaked online chat in which he and top aides exchanged obscenity-laced messages.
He said he would leave office next year, at the end of his term.
But protesters have said he must stand down immediately and the number of marchers on the streets has increased.
The leaked text messages included homophobic slurs as well as insults about victims of the deadly Hurricane Maria in 2017.
Asked about the matter, US President Donald Trump said Mr Rosselló was "a terrible governor".
"You have totally grossly incompetent leadership at the top of Puerto Rico," he told reporters at the White House. "The leadership is corrupt and incompetent."
Footage early on Monday morning showed crowded trains headed to the capital, and long lines of protesters preparing to march in the sweltering Caribbean heat.
Some protesters were seen blocking highways while chanting "Ricky resign". The hashtags #RickyRenuncia ("Ricky resign") and #ParoNacional (national strike) both trended on Twitter.
Experts predicted the crowd size would eclipse the largest protest in the island's history 15 years ago, when Puerto Ricans successfully petitioned the US military to end training missions on the island of Vieques.
What are the secret messages?
The chat, which contained 880 pages of exchanges between the governor and 11 all-male allies, was leaked on 13 July and has led to days of protests outside the governor's mansion in San Juan.
Several of the texts mock victims of Hurricane Maria, which devastated the island in 2017, and may have led to more than 4,000 deaths.
In one instance, Mr Rosselló criticised the former speaker of the New York City Council, Melissa Mark-Viverito, saying people should "beat up that whore".
When the island's chief fiscal office wrote that he was "salivating to shoot" the mayor of San Juan, Mr Rosselló replied: "You'd be doing me a grand favour."
What has the governor said?
On Sunday, the 40-year-old governor refused to resign, but said he would step down as leader of the New Progressive Party, a Puerto Rican political party which advocates for US statehood.
In an attempt to appease protesters, he said he would not seek re-election.
"I hear you," Mr Rosselló said in a Facebook video. "I have made mistakes and I have apologised."
"I know that apologising is not enough," he said.
"A significant sector of the population has been protesting for days. I'm aware of the dissatisfaction and discomfort they feel. Only my work will help restore the trust of these sectors."
What has the reaction been?
The island's largest newspaper, El Nuevo Día, called on the governor to resign in its Monday editorial.
"Puerto Rico has spoken up, not only as a strong, broad and united voice, but as the right voice," the editorial said. "With a gesture of nobility and humility, Governor, it is time to listen to the people. You have to resign."
San Juan Mayor Carmen Yulin Cruz said in a Twitter message on Monday: "They can't deny it: The power is in the street."
Singer Ricky Martin, who was targeted in the secret messages, was among those calling for the governor to resign, as well as Hamilton creator Lin-Manuel Miranda and reggaeton star Bad Bunny.
"They mocked our dead, they mocked women, they mocked the LGBT community, they made fun of people with physical and mental disabilities, they made fun of obesity. It's enough. This cannot be," Martin said in a video on Twitter.
What are US media saying?
The island's political crisis has made headlines throughout mainland US.
The New York Times editorial board wrote that the "callousness and partisan self-dealing" exposed by the messages serve as exorbitant strain for the long-suffering island, effectively "rubbing salt into a long-festering wound".
"The Puerto Rican people have no use for petty political feuding," the New York Times wrote. "Their territory is struggling under the weight of government corruption, incompetence and indifference. Having been failed by their leaders at every level, they are out of patience. They deserve better."
Similarly, the editorial board for the Washington Post said that while Puerto Ricans may be aware that the mainland treats them "like second-class citizens", the messages are evidence that their local government also regards them with contempt.
And the island's problems run much deeper than Mr Rosselló, the Post wrote.
"It is clear that the island's problems won't be solved simply with his departure. Serious, systematic reform is needed."
Indeed, several outlets described the scandal as a consequence of foundational failings among Puerto Rico's political class.
"You may think the protests erupting in Puerto Rico are all about the government's texting scandal," CNN reported. "But the problems run much deeper."
The last two weeks "are just the culmination of the worst political crisis in modern Puerto Rico's history", a journalist for NBC wrote. "All of this dysfunction is a product of a corrupt (mostly white, mostly privileged) political class that has ruled the island for decades."