NDP Leader Dominic Cardy will run in the Nov. 17 Saint John East byelection, making it his third attempt at a seat in the legislature in two years.

NDP Leader Dominic Cardy resigned his party's leadership on Sept. 22 after he failed to win a seat in the legislature. (CBC) The sudden resignation of Liberal Gary Keating, who won the riding, has prompted Cardy to put on hold his plan to quit as his party's leader, a decision he announced on election night.

"I absolutely felt it was the appropriate thing to do," Cardy told CBC News on Tuesday afternoon. "The party has made it very clear they did not think that was the case and have said they believe I was the strongest person to fly the NDP flag going into this byelection."

Cardy says his wife didn't accept his resignation and was key in his decision to stay on as party leader.

"It's been pretty humbling the past few weeks," he told CBC's Harry Forestell. "Both the disappointment of election night and the outpouring of support since then. Especially the folks on the ground in Saint John East and our great candidate Phil Comeau."

On Tuesday evening, Cardy sent out a press release saying he would launch his campaign for the Saint John East byelection at noon on Wednesday, October 22.

Keating won the Saint John East riding for the Liberals by nine votes, the narrowest margin in last month's provincial election.

NDP candidate Phil Comeau finished in third spot with 1,167 votes, compared to 2,332 for Keating and 2,323 for Tory Glen Savoie.

Keating stunned many in the riding 22 days later when he announced he could not fulfill his duties as the riding's MLA.

The Liberal cited the negative impact being an MLA would have on his family and health.

Premier Brian Gallant wasted little time in calling the byelection for Nov. 17.

The Liberals recruited Saint John Deputy Mayor Shelley Rinehart, a business professor at the University of New Brunswick, to run in the byelection.

Saint John Deputy Mayor Shelley Rinehart announced on Monday morning that she would run for the Liberals in the Saint John East byelection (CBC) The Tories are fielding a familiar face in the upcoming byelection.

Savoie will run again for the Progressive Conservatives. Savoie was elected in the former riding of Saint John Fundy in 2010. He will be officially nominated tonight.

J.P. Lewis, a political scientist at the University of New Brunswick in Saint John, said Savoie may have the most to gain on Tuesday because of Cardy's announcement.

“Because the NDP placed a strong third at almost 20 per cent in this riding in the general election, Cardy’s entry is not good news for the Liberals," Lewis said.

"Even if Cardy doesn’t win, a strong showing could allow Glen Savoie to sneak up the middle with 35 per cent of the vote, which is below the number he attained in the general election, which was 37 per cent,” Lewis said.

Cardy's third chance at a seat

This will be Cardy's third attempt to win a seat in the legislature, in his third different riding, since 2012.

The NDP leader first sought a seat in the legislature in 2012, when he ran in the Rothesay byelection.

Cardy finished in third place behind Tory Ted Flemming and the Liberals.

In September's election, Cardy set his sights on his home riding of Fredericton West-Hanwell.

J.P. Lewis, a political scientist at the University of New Brunswick, said it is not surprising that Cardy decided to run in the Saint John East byelection. (CBC) ​Cardy improved his performance from the Rothesay byelection by finishing in second spot, but once again lost to the Progressive Conservatives.

As a provincial leader, Cardy spent much of the campaign in other ridings trying to drum up support for his party's candidates. The NDP saw its overall share of the popular vote rise to 12.9 per cent, from 10.3 per cent in 2010 but it remained shut out of the legislature.

The NDP leader will be again looking to the Saint John area as a landing spot.

UNB's Lewis said Cardy is risking very little by jumping into this latest campaign.

“He is risking being called an opportunist and going back on his intention to resign, but we are naïve to think this is novel in electoral politics. Changing minds, running in different ridings, having strategic approaches to byelections has been going on for years and will continue to go on," Lewis said.

"In fact, considering the circumstances, it may have been more surprising if he didn’t run. If his intentions truly were to leave New Brunswick politics then all he’s risking is losing another election."

Saint John has been willing to elect NDP members in the past. Former leader Elizabeth Weir held the riding of Saint John Harbour from 1991 to 2005.

Peter Trites won the riding of East Saint John in a 1984 byelection.

The NDP has been shut out of the legislature since 2005, when Weir resigned to become the first president and chief executive officer of Efficiency New Brunswick.

Green Party Leader David Coon was able to win his own riding in Fredericton South.

Sharon Murphy will run for the Greens in Saint John East. She finished in a distant fourth position on Sept. 22 in the riding with 353 votes.

The People's Alliance will announce its candidate for the byelection later this week.