TROIS-RIVIERES, Que. -- Justin Trudeau would not say Thursday whether his team asked former U.S. president Barack Obama to endorse his bid to remain prime minister, which came as the Liberals fight hard to convince progressive voters to stick with them.

"Barack Obama makes up his own mind," Trudeau said during a campaign stop in Trois-Rivieres, Que., when asked directly if he sought the endorsement.

The day before, Obama voiced his support for Trudeau on Twitter as the clock ticks down to the Oct. 21 vote, with public opinion polls suggesting either the Liberals or the Conservatives could form a minority government.

Trudeau has been working hard to convince progressive voters to cast their ballots for the Liberals, as the polls also suggest many are leaning toward the NDP and the Greens, and, in this province, a resurging Bloc Quebecois.

The friendly nod from the past U.S. president has also sparked some controversy at a time when concerns about foreign interference in democratic elections is top of mind for many governments and voters.

"I was happy to be able to work alongside Barack Obama on important issues around the globe, including, significantly, the fight against climate change, and I'm working really hard to be able to continue that work over the next four years," Trudeau said when asked Thursday how the endorsement came about.

"I was obviously happy to hear his words yesterday, but nobody tells Barack Obama what he should do," he said.

Trudeau was also asked whether he had apologized to Obama, the first African-American to be elected U.S. president, for having worn brown- and blackface in the past.

Trudeau responded by saying the last time he spoke to Obama was in the spring when the former president, who also previously endorsed Emmanuel Macron's successful bid for the French presidency, delivered a speech in Ottawa.

Last month, Time magazine published a photo of Trudeau in dark makeup at a 2001 "Arabian Nights" party organized by West Point Grey Academy, the Vancouver private school where he was a teacher. The photo was in the school yearbook.

Two more instances of Trudeau wearing blackface quickly emerged.

Trudeau has apologized for wearing the makeup, which he says he now believes is racist.

Trudeau spent Thursday campaigning in Quebec, where the Liberals won 40 of 78 seats in 2015, which played a major role in delivering them a majority government.

The sudden rise of the Bloc Quebecois is posing a threat to their ability to form another one, which is one reason Trudeau has been going extra hard against the party in his messaging.

Liberal candidate Francois-Philippe Champagne, a cabinet minister seeking re-election in Saint-Maurice--Champlain, decried the argument from the Bloc Quebecois that they can be a stronger voice for the province.

"Does anyone believe that?" Champagne said in Trois-Rivieres on Thursday.

"Honestly, I would say I think Quebecers want to decide for themselves and deciding for yourself is being in government," he said.

"The nature of the opposition is asking questions in the House. The nature of government is to govern, is to reflect what Canadians want, so I'm very confident that Quebecers want to decide for themselves," he said.

While some of the post-election discussion has started to shift toward the scenarios in which either the Liberals or Conservatives would be able to form a minority government, Trudeau refused to weigh in, saying he remained focused on winning a strong Liberal government.

This report by The Canadian Press was first published Oct. 17, 2019.