BRASÍLIA — As she fights for her political life, President Dilma Rousseff has been tirelessly describing the drive to remove her from office as nothing less than a coup.

In a country with bitter memories of military dictatorship — the most recent one having given way to civilian rule in 1985 — the word is especially fraught, and it has become a rallying cry that has energized supporters who are battling to stave off an impeachment trial in the Senate that could begin as early as next month.

“I am the victim of a process that is rooted in injustice, and legal and political fraud,” she said during a news conference on Tuesday, two days after the lower house of Congress voted by a wide margin to approve an impeachment measure.

The debate about removing her from office, which is convulsing a polarized nation, centers on a crucial question: Did she commit an impeachable offense?