Mainstream Brazilian news outlets criticized her decision to seek international support in her fight against impeachment, describing it as a move that would besmirch the nation’s image.

“From her palace bunker, the president seems to feed the bizarre belief that the international press is prone to support her,” Folha de S. Paulo, one of the nation’s leading newspapers, wrote in an editorial. “This is a bad step, and Dilma Rousseff will only shake a little bit more, with her diplomatic negligence, the image of Brazil as a dynamic and stable democracy.”

Her opponents in Congress began a parallel public relations campaign, dispatching two deputies to New York. And Vice President Michel Temer, who would temporarily replace Ms. Rousseff during an impeachment trial, gave a series of rare interviews to the foreign media to express his concern over her decision to travel to New York.

Throughout the day, the president was shadowed by the two deputies, who sought to counter her arguments that the impeachment proceedings are a threat to Brazil’s young democracy.

“If this is a coup, how is it that she left the country and allowed her vice president to fulfill her duties?” José Carlos Aleluia, a federal deputy from the opposition Democrats Party, said in an interview. “The military is in the barracks, and when she returns to Brazil, she will once again be president.”

In another sign of her sinking fortunes, members of the nation’s highest court, which has already rejected appeals to have the impeachment petition quashed, added their voices to those criticizing her visit to New York, suggesting that future appeals to the court have little chance of succeeding.

“The responsible response would be to make a defense that respects Brazilian institutions and transmit a positive message about Brazil to the world — that it is solid democracy that works and that it’s institutions are responsible,” José Antonio Dias Toffoli, a Supreme Court justice, told Brazilian reporters on Wednesday.