Brazil's Senate is poised to vote Wednesday on whether to impeach President Dilma Rousseff on charges that she violated budgetary rules.

The country's House of Representatives already voted in favor of impeachment, with well more than the required two-thirds majority. The speaker of the House said Monday that he would annul that vote, blaming "politics" for the decision — but he later reversed his decision.

Now it's in the hands of Brazil's 81 senators. They're widely expected to vote in favor of impeachment, even though, as NPR's Lourdes Garcia-Navarro has explained, many legal analysts view the case against Rousseff as "insubstantial."

Here's how The Associated Press puts it:

"The charges against her were obscure, not the variety that spurs outrage: She is alleged to have broken fiscal rules in her handling of the federal budget to hide deficits and bolster an embattled government. The allegations also came with a good dose of irony: Her main opponents in Congress are accused of crimes much worse."Yet what started as a long-shot bid has gained momentum and, as the Senate prepares to vote Wednesday on whether to put her on trial, many analysts consider Rousseff's ouster all but a foregone conclusion."

In addition to the charges of tampering with the budget, Rousseff has also been accused of involvement in a vast corruption scandal involving state oil company Petrobras, as we've reported on the blog, but those allegations are not a part of the impeachment proceedings.

According to the Brazilian newspaper Folha de Sao Paolo, 50 senators have expressed their intention to vote for impeachment.

That's well beyond the simple majority vote — 41 — that would result in Rousseff's suspension for up to 180 days during a trial. And it's not far from a two-thirds vote — 54 — that would remove her permanently from office.

Either way, Brazilian Vice President Michel Temer would step in to fill her shoes.

Temer, a 75-year-old constitutional lawyer, is "a behind-the-scenes deal-maker whose strength is making alliances," Catherine Osborn reported on Morning Edition.

He has moved up through the ranks of several ruling governments in Brazil — "but what his allies laud as canny negotiating, his critics say is rank opportunism," Osborn says. Only 2 percent of Brazilians say they would vote for Temer in a presidential election, she notes.

And the vice president has been accused of corruption.

"Unlike Rousseff, who has not been accused of personal enrichment, Temer is accused of being involved in an illegal fuel purchasing scheme, part of the huge graft scandal at state oil company Petrobras," Osborn noted.

As we've previously reported, the speaker of the House, who would be next in line for the presidency, is also linked to charges of corruption.

The vice president and House speaker are certainly not alone. BBC Brazil reported on the makeup of the Senate that is voting today — noting 58 percent of lawmakers are under investigation for improper conduct or corruption.

(Political dynasties are also well represented — 60 percent of the senators have family members in politics. And 13 percent of the senators are unelected, that is, filling the seat of an elected senator who has left his or her duties. BBC Brazil notes that family members or major campaign donors often step in to fill a departing senator's seat.)

Rousseff has denied the charges against her and characterized the impeachment as a "coup."

On Tuesday, Rousseff's government made a final effort to block the impeachment by appealing to the nation's supreme court, the AP reports. But so far, the wire service writes, the court has "mostly steered clear of direct involvement" in the process.

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