Mercedes Araoz had sworn the presidential oath a day earlier before dozens of dismissed lawmakers who designated her to replace Vizcarra temporarily. The opposition had suspended Vizcarra on the grounds he had violated the constitution in his push to strong-arm lawmakers into backing his anti-graft proposals.
But no state institution or foreign power has recognized Araoz as interim president. Instead, the military and police reaffirmed their loyalty to Vizcarra and politicians who support him formally accused her of trying to usurp his functions.
It was a stunning turn for Peru's relatively young democracy, which just two decades ago saw the country's authoritarian former president Alberto Fujimori resign as a mounting graft scandal paralyzed his rightwing government.
In a late-night post on Twitter, Araoz said she had reconsidered her role at the center of the dispute, pointing to a regional body that had appeared to back Vizcarra in the dispute earlier in the day.
Araoz announced her resignation from the vice presidency as well as the interim presidency. "I hope my resignation leads to...general elections as soon as possible for the good of the country," she said.
The announcement took many by surprise. Pedro Olaeachea, the recently-dismissed president of Congress, was in an interview with CNN Espanol when the broadcaster's reporter read him Araoz' resignation letter to him, appearing to leave him speechless for a moment.
CRIMINAL PROBES
With Araoz out, an influential former lawmaker, Rosa Maria Bartra, said that in the opposition's view Olaeachea should assume the interim presidency and oversee a transition to new general elections.
But that plan might come to naught if the country's electoral authorities merely ignore any summons to organize an election.
A majority of Peruvians in recent polls backed the dissolution of Congress, and thousands of his supporters took to the streets late on Monday to pressure holdout lawmakers to leave the building.
It was not clear how many dismissed members of Congress remained in the chamber, after some left and police in riot gear barred them from reentry. Streets around Congress were on lockdown on Tuesday.
Vizcarra has blamed the opposition party led by Fujimori's daughter - jailed former presidential candidate Keiko Fujimori - of deploying anti-democratic tactics in order to shield a corrupt network of politicians from fast-moving criminal probes.
The Organization of American States, which aims to promote democracy in the Western Hemisphere, said only Peru's Constitutional Tribunal could determine the legality of Vizcarra's dissolution of Congress.
But it also appeared to back his schedule for new legislative elections.
"It's a constructive step that elections have been called in accordance with constitutional timeframes and that the definitive decision falls to the Peruvian people," the office of the OAS said. "The political polarization the country is suffering can be resolved at the ballot box."