When Canadian Prime Minister Justin Trudeau took office in late 2015, he was a political golden boy who seemed destined to build on the legend of his father. But six months ahead of an October election, polls suggest the 47-year-old politician could become the first prime minister to lose power after a single majority mandate since the 1930s.

Trudeau is mired in a relentless scandal over alleged interference in a corporate corruption case that has led to the resignations of two Cabinet members, his top advisor and the head of the federal civil service.

The ruling Liberals have lost 6 percentage points since the start of the year, ceding the lead to the rival Conservatives, according to a Nanos Research poll published on Tuesday.

If an election were held now, the Conservatives would win 34.9 percent of the vote, the Liberals 32.8 percent and the left-leaning New Democratic Party 16.6 percent. The poll suggests the result would be deadlock or a fragile minority government.

"The Liberals have taken a hit, but they're still competitive," said pollster Nik Nanos. "The most significant effect has been the negative impact on the prime minister's personal brand.”

An Ipsos poll from last month put the Conservatives at 40 percent, 10 points ahead of the Liberals.

Trudeau, the oldest son of the late Prime Minister Pierre Trudeau, has from the start pushed a progressive agenda in support of gender equality, the environment and aboriginal rights, all issues that appeal to his core voters, but which after more than three years sound increasingly scripted to some.

Trudeau is not helped by the optics of the scandal involving SNC-Lavalin Group Inc, a prominent Montreal-based engineering and construction firm that has been accused of bribing Libyan officials to get contracts between 2001 and 2011.

The prime minister has been on the defensive over allegations government officials inappropriately pressured Canada's former Justice Minister Jody Wilson-Raybould to drop a criminal case against the company in favor of a deferred prosecution agreement, or out-of-court settlement.

Wilson-Raybould, the first indigenous justice minister in Canadian history, resigned over the scandal. Former Treasury Board chief Jane Philpott also quit in protest. They were two of the highest-profile women in Trudeau's Cabinet.

So far, Trudeau's strategy appears to have changed little, and people close to him say he plans ride it out without major shifts in strategy.

"Successful politicians know when to pivot, and they have a strong survival instinct," Nanos said, calling the scandal the "first major test of Justin Trudeau's leadership".