Over the past year, U.S. President Joe Biden has deployed top administration officials to meet with their Brazilian counterparts and convey a simple message to President Jair Bolsonaro: Don’t derail Brazil’s democracy.

Top officials from the White House, Defense Department, State Department, and even the CIA have held meetings and calls with Brazilian officials to try to head off any efforts by Bolsonaro to subvert the results of the country’s heated presidential elections.

The diplomatic surge comes as the right-wing populist Bolsonaro faces off against left-wing candidate and former President Luiz Inácio Lula da Silva in a hotly contested runoff vote in what has proved to be one of the most divisive elections in the country’s history. The latest polls show Lula with a slight edge over Bolsonaro.

Bolsonaro, taking a page from the playbook of former U.S. President Donald Trump, has tried to cast doubt on the trustworthiness of the upcoming vote by claiming without evidence that the country’s electronic voting system has a history of fraud and that parts of the country’s independent judiciary favor Lula in the race.

Lula beat Bolsonaro in the first round of elections in early October but failed to win by a high enough margin to avoid a second round of elections. The final vote takes place on Oct. 30. Bolsonaro has for months cast doubt on the security of Brazil’s polling machines and urged his supporters to “go to war” if the election is “stolen.”

For Team Biden, the playbook from a man sometimes called the “Trump of the Tropics” looks all too familiar. Bolsonaro’s efforts to lay the groundwork for an election challenge mirrors Trump’s efforts to cast doubt on the 2020 U.S. presidential election results, a campaign that culminated in a deadly pro-Trump mob attacking the U.S. Capitol on Jan. 6, 2021, with an eye to violently overturn the election results.

Some experts and former officials believe that despite the high tensions in the hotly contested election, Brazil’s democratic institutions have strong enough guardrails to protect against any possible power grab or efforts to undermine the results by Bolsonaro.

“It will be a stress test for Brazil’s democratic institutions and one that we have never had since Brazil transformed to democracy in the 1980s,” said Pedro Abramovay, the Rio de Janeiro-based director of the Latin America program at the Open Society Foundations and a former Brazilian justice ministry official during Lula’s presidency, from 2003 to 2010.

“Brazilian democracy since the late 1980s has just gone from strength to strength,” said Michael McKinley, the U.S. ambassador to Brazil from 2017 to 2018.

Still, the U.S. diplomatic campaign in Brazil underscores how worried the Biden administration is that Bolsonaro could refuse to accept defeat in the upcoming vote and offers a window into how the post-2020 election violence at home has left its imprint on Biden’s foreign-policy team.