By BLOOMBERG

WASHINGTON • Justin Trudeau’s (picture) popularity among voters faces a fresh test after the US left his top diplomat out of recent Nafta talks with Mexico.

While the Canadian prime minister does well in opinion polls when taking on President Donald Trump, he also knows he needs to dispel the perception he’s more about flash than substance.

Both factors will be in play as Canada responds to the Trump administration’s new focus on talks with Mexico.

Trudeau’s team, led by Foreign Minister Chrystia Freeland, has been rebuffed in recent attempts to discuss changes to the North American Free Trade Agreement (Nafta), according to three people with knowledge of the negotiations.

The push with Mexico may simply reflect US Trade Representative Robert Lighthizer’s desire for a breakthrough on the crucial issue of rules for car production. The US wants provisions that would blunt the advantage Mexico enjoys due to cheaper wages.

But Trump has made clear his preference for one-on-one deals with countries, which he believes gives the US a negotiating edge. And less than two months ago, the president unleashed a Twitter tirade against the Canadian prime minister, calling him “very dishonest and weak” after Trudeau said he would push back against US steel tariffs at a Group of Seven summit in Quebec.

Canada hasn’t been excluded from the talks, according to a Canadian government official who asked to remain anonymous because the negotiations are private. The country encourages the US and Mexico to talk to each other, and in order for the three countries to reach an agreement, the US and Mexico largely have to sort out issues between them, autos being the primary one, the official said.

Even though Nafta is trilateral, the negotiations themselves have largely been bilateral, the official said, adding Freeland and Lighthizer mutually agreed last week there was no reason for Canada to participate this week because the focus was on the US and Mexico.

David MacNaughton, Canada’s ambassador to the US, said the Nafta talks are progressing well and the auto issue appears close to being resolved. Some of the remaining issues need to be addressed in bilateral talks, while others will require all three countries, he said.

“I’m hoping we can get it done as quickly as possible, and we will be at the table working 24-7 if we have to to make it happen,” MacNaughton said in an interview on Wednesday. “It would be great to be get it done by the end of August.”

After Trump’s barrage, voter support for Trudeau’s Liberals jumped to the highest level since they won the 2015 election, according to polling by Nanos Research. The surge helped Trudeau recover from a bumbling trip to India in February, where he was mocked for parading through the country in a range of traditional Indian outfits.

Getting frozen out by the US risks reinforcing the view that the 46-year-old prime minister, who has graced the cover of GQ magazine and is known for tweeting photos of his socks, doesn’t have the mettle to negotiate a good deal for Canada.