Brazilian President Dilma Rousseff launched a last-minute bid today to block impeachment proceedings against her in what could be her final hours in power.
Her lawyers said they would appeal to the Supreme Court to annul the impeachment proceedings before the Senate gathers tomorrow to vote on whether to suspend her from office and launch an impeachment trial.
The result of what is expected to be a marathon voting session may not be final until Thursday.
If she is pushed out, her vice-president-turned-enemy Michel Temer will take over.
Adding to the instability shaking Latin America's most populous country and biggest economy, the leaders of the Senate and the lower house spent yesterday in open conflict on whether the vote should go ahead at all.
Late yesterday, the interim speaker of the lower house, Waldir Maranhao, backed down and reversed an earlier attempt to order the Senate to halt proceedings and return Rousseff's case to the lower chamber.
That eased what was looking like an institutional crisis, until state attorneys said in a statement today they would request "the annulment of the impeachment process" by the Supreme Court.
There was no patching over the divisions left in Brazil by the trauma of what Rousseff is daily denouncing as a coup d'etat.
Lawmaker Jose Guimaraes, from Rousseff's leftist Workers' Party, said that despite almost certain defeat in the initial Senate vote, the impeachment trial itself would be an all-out fight.
"We will have 180 days in the Senate, talking with every one of them, to get them to change their minds," he told journalists, warning that "our main fight today will be in the streets."
Police are responding to heightened tensions by building a huge metal barricade outside Congress in the capital to separate rival groups of protesters during the Senate vote. A separation corridor 80 meters (yards) wide and more than a kilometer (half-mile) long will also be enforced.
A square where major government institutions are located will be declared a "national security zone" and made off-limits to the public, Brasilia security authorities announced.
Huge anti-government protests and smaller but still significant pro-Rousseff rallies have been a regular feature in Brazil over the last year but so far have passed off peacefully.
