SAN JUAN, Puerto Rico (AP) — Puerto Rico Gov. Ricardo Rosselló resigned Friday as promised, clearing the way for veteran politician Pedro Pierluisi to be sworn in as his replacement, a move that threw the U.S. territory into a period of fresh political uncertainty.

Rosselló had promised to step down in response to weeks of popular protest over mismanagement and a series of leaked chats in which he and advisers denigrated a range of Puerto Ricans. Because of problems with the qualifications of members of Rosselló’s administration in the constitutional line of succession, it was unclear until the last minute who would become governor.

Pierluisi was named secretary of state, the next in line to be governor, in a recess appointment this week. In an emailed announcement from his office, Rosselló said Pierluisi would succeed him. He was sworn in by a judge at 5 p.m., the hour Rosselló had set to leave office.

Four hours later, San Juan Mayor Carmen Yulín Cruz tweeted that the municipality at 8 a.m. on Monday would be challenging Pierluisi’s swearing in as governor. Meanwhile, a well-respected attorneys’ organization accused Pierluisi of “hijacking” the constitution.

The territory’s House of Representatives confirmed Pierluisi as secretary of state Friday, but the Senate has not yet voted on his appointment. Rosselló said confirmation by both houses was unnecessary for a recess appointment, an assertion that appeared certain to generate legal challenges.

After taking the oath at his sister’s house, Pierluisi emerged at the governor’s residence to address the press and promised only to serve as governor until the Senate’s hearing on his nomination, which has been moved up to Monday. If the Senate votes no, Pierluisi said, he will step down and hand the governorship to the justice secretary, the next in line under the constitution.

Nothing more was heard from Rosselló.

Pierluisi said he was “fully capable and authorized to act, but the Senate will have its say.”