Kellie Leitch saw her first-choice support among Conservative party members almost double last week, according to the latest iPolitics CPC Leadership Tracker, powered by Mainstreet Research.

Maxime Bernier, meanwhile, dropped to his lowest first-choice support since Mainstreet started tracking the race.

From March 15 to 19, Mainstreet reached 1,105 members and found — with a margin of error of +/- 2.8 per cent, 19 times out of 20 — Kevin O’Leary was the top candidate for 22.10 per cent of members, down from 23.65 per cent last week.

Leitch came close to doubling her support, from 8.53 per cent to 16.89, catapulting her ahead of Maxime Bernier. At 14.73 per cent, Bernier’s first-choice support was his lowest yet.

In the previous poll, he was at 19.29 per cent. Andrew Scheer (9.16 per cent), Lisa Raitt (7.82 per cent), and Michael Chong (5.48 per cent) rounded out the top six.

Bernier’s drop came with a corresponding rise in his least-likely to support number. At 16.53 per cent, he’s now second in the dubious category behind O’Leary.

So what’s behind Leitch’s rise and Bernier’s decline? Mainstreet Research President Quito Maggi thinks the most obvious answer is the ongoing controversy that surfaced last week over fraudulent party members.

Last Thursday evening, Kevin O’Leary’s campaign alleged membership fraud, which was subsequently confirmed by the party. Though O’Leary never accused any campaign specifically, Bernier’s team put out a press release on Friday calling O’Leary a “loser” who was throwing mud instead of trying to win people over.

The Bernier campaign then accused one of O’Leary’s key Sikh-Canadian organizers of having offered to pay for party memberships, which is against party rules.

“We stayed in the field an extra day — until Sunday — because all this noise happened at the end of the week. We wanted to see if this would have an effect. Sure enough, you see it,” Maggi said.

“O’Leary made a claim about vote rigging the night before. By coming out and calling him a loser the next day, it was almost an admission from Bernier’s team that the complaint was about them, even though nobody knew who it was traced to.”

Maggi added that Bernier’s approach was a departure from what’s been a policy-driven campaign.

“I think one thing about Bernier that’s been consistent throughout … he hasn’t tried to pick fights. He’s been the guy talking about policy. This is the first fight he’s tried to pick, but it was a big one. I think, to a certain extent, it backfired,” he said.

For whatever reason, it was Leitch whose first ballot support increased the most this week.

“She seems to have stolen a bit from everybody,” Maggi said.

With each riding worth 100 hundred points, however — regardless of how many members it has — the first-ballot choice doesn’t provide a complete picture.

Looking at first-ballot points, second and third-ballot support, and regional support, it remains a two-way race between O’Leary and Bernier.

“Bernier still leads on second and third choice, just like he has consistently throughout. Though he is down slightly overall,” Maggi pointed out.

“Whether this membership fraud noise gets drowned out by the federal budget being tabled tomorrow, we’ll see next week. Maybe something external to the race actually helps dampen the effect. But if it wasn’t for the budget happening tomorrow, I would bet that this war of words would continue escalating.”

The iPolitics CPC Leadership Tracker, powered by Mainstreet, will be tracking the Conservative leadership race until members pick the next leader on May 27. For additional information on methodology and to subscribe to in-depth updates, click here.