Open this photo in gallery:

Alberta Premier Danielle Smith has lagged in polls and continues to deal with the fall-out of a by-election loss in Calgary’s conservative heartland.Darren Calabrese/The Canadian Press

Premier Danielle Smith’s United Conservative Party and Alberta NDP Leader Naheed Nenshi ramped up their political attacks on each other this week as the province entered the home stretch of its referendum campaign.

On Thursday, while Ms. Smith basked in the afterglow of a West Coast pipeline being declared a project of national interest, she also took a swipe at Mr. Nenshi over federal NDP Leader Avi Lewis’s strong opposition to the proposed conduit.

Mr. Nenshi piped back with criticism of his own after it emerged earlier this week that one of Ms. Smith’s caucus members had voted by mail in favour of a second, binding vote on secession, as separatist leanings within her party continue to cause turmoil and weigh down the Premier’s popularity.

Gary Mason: The ugly reckoning coming for Danielle Smith

While the Oct. 19 referendum has consumed Alberta’s political scene this fall, Ms. Smith and Mr. Nenshi are preparing to spend much of the next year in campaign mode ahead of the October, 2027, provincial election.

Recently, Ms. Smith has lagged in polls and continues to deal with the fall-out of a by-election loss in Calgary’s conservative heartland. Inside her party, she is managing an uprising of separatist sentiment and pockets of discontent among UCP membership over her federalist stand.

Mr. Nenshi, on the other hand, has been buoyed by the NDP’s surprise by-election win. But Mr. Lewis’s disapproval of the West Coast pipeline and earlier vows to stop the expansion of oil and gas development have forced Mr. Nenshi to respond, opening his own party to familiar attacks from conservatives.

Open this photo in gallery:

Alberta NDP Leader Naheed Nenshi has been buoyed by the party’s surprise by-election win.JASON FRANSON/The Canadian Press

On Thursday, Ms. Smith and Prime Minister Mark Carney met their shared deadline to designate a proposed pipeline to the West Coast a project of national interest.

The Premier has heralded the pipeline as proof of Alberta’s renewed relationship with Ottawa, less than three weeks before Albertans decide on remaining in Canada or working toward a binding secession vote.

But the announcement was overshadowed by news that one of Ms. Smith’s caucus members, Jason Stephan, had voted for holding a second, binding referendum on separation.

He described the choice as one that “puts Ottawa on notice,” while voting to remain in Canada “affirms the status quo, a nation in decline, dragging Alberta down with it.”

On Thursday, Ms. Smith – who says she will vote to remain in Canada – said she welcomes a variety of opinions in her party.

Mr. Stephan remains a member of caucus. He did not respond to a request for comment.

The pipeline announcement, meanwhile, reignited a dormant conflict between the federal and provincial NDP, which have long warred over their positions on oil-and-gas development.

Opinion: We must call Alberta separation what it is

Mr. Lewis criticized the plan as a “pipeline to the courts” and “another gift to the oil industry,” while Mr. Nenshi applauded the news: “I’m looking forward to actually getting it built in conjunction with the strongest environmental safeguards in the world,” he said on Friday.

Ms. Smith latched on to Mr. Lewis’s comments, calling on Mr. Nenshi to break with the federal NDP – “right down to the name of their party,” she wrote.

Asked about Ms. Smith’s call to change the party name, Mr. Nenshi said: “If you’re giving me advice on my party, I’ll give you some on yours: Kick out the separatists.”

Mr. Lewis’s stand against oil-and-gas development has appeared to widen the chasm between the national party and its provincial counterparts, many of whom are competing to win their respective governments. Mr. Nenshi and Saskatchewan NDP Leader Carla Beck both denounced his plans for the sector when he was elected party leader in March.

“We’ve cut that tie with the federal NDP, and fundamentally, he can say what he likes,” Mr. Nenshi said of Mr. Lewis on Friday, referring to the provincial party’s decision in 2025 to make federal party membership optional.

Mr. Nenshi had previously appealed to Mr. Lewis and the other contenders running for federal party leadership to not damage his 2027 election campaign.

Opinion: Mark Carney is an Albertan. That’s about to pay off

On Friday, Mr. Nenshi dismissed Ms. Smith’s efforts to link him to the federal party leader.

“They would like nothing more than to tie me to Avi Lewis, and it’s been completely unsuccessful so far, and it will continue to be completely unsuccessful,” he said.

Anne McGrath, principal secretary to former Alberta NDP premier Rachel Notley, said in an interview that tension between the federal and Alberta NDP over pipeline development is an enduring feature of New Democratic politics.

Ms. McGrath, also a former campaign director for the federal NDP, said she believes the public understands the differences between the national and provincial parties.

“I think that they understand that tension. They live in that tension,” said Ms. McGrath of the Alberta NDP.

“But they, I don’t think are going to spend a lot of time raising hell about it or anything like that.”