Gerard Deltell of the Coalition for Quebec's Future will seek the Tory nomination in the Quebec City riding of Louis-Saint-Laurent.
Deltell, 50, has represented the riding of Chauveau since 2008, at first for the now-defunct Action democratique du Quebec and, since 2012, for the Coalition.
"I am blue, true blue, an old blue," he told a news conference Tuesday at which he took out his Conservative membership card from the 1980s
"I'm coming home and I'm really happy about it."
The Tories won five out of 75 seats in Quebec in 2011 after winning 10 three years earlier.
If, as expected, Deltell does win the nomination, his experience would likely stand him in good stead in this fall's federal election and could serve as a springboard for the Conservatives in the Quebec City region.
Harper welcomed Deltell's jump.
"Obviously, I am very encouraged by Mr. Deltell's interest," the prime minister said at an event in British Columbia.
"I think his candidacy and that of others indicates that Quebecers are increasingly recognizing their priorities in our party."
Deltell said he will forgo a severance payment of $114,000 as well as a total of $388,000 in pension to which he would be eligible over the next 15 years.
He insisted in a later interview he won't touch any of the $500,000 even if he doesn't land the nomination or doesn't become an MP.
The amount is roughly what it will cost to organize the byelection to replace him.
Deltell was asked about leaving provincial politics just a year into his mandate — the Quebec vote was held last April 7 — and forcing the government to call the costly byelection.
Deltell said switching to federal politics was not in his initial plans and that he finally made the decision after listening to constituents who urged him to take the plunge.
The former journalist will not be acclaimed the Tory candidate in Louis-Saint-Laurent. Nathalie D'Amours, the former president of an association that represents daycare workers, announced on Facebook a few days ago she would seek the nomination.
Alexandrine Latendresse won the riding for the NDP in 2011 with a narrow margin but has announced she won't seek re-election. G. Daniel Caron, a former Canadian ambassador to Ukraine, will represent the party.
Caron wasn't too impressed by the timing of Deltell's announcement.
"Everybody knew there would be a federal election in 2015 so it's a bit cynical to have run provincially and to abandon his constituents like that," Caron said.
"Choosing the anniversary date of his election in Chauveau to make the announcement is a bit surprising."
Deltell said he has not been promised a cabinet post should the Conservatives stay in power. Four of the party's current five MPs from Quebec are in cabinet.
"Absolutely not," he said in the interview. "I'm not asking for anything and I'm not being given any promises."
A spokeswoman for Deltell's current party said it will remain neutral come the fall.
"Elected members of the Coalition have no intention of getting involved in the federal campaign," Emilie Toussaint wrote in an email.
"It will be up to Quebecers to decide who they send to Ottawa and we will work with whoever they choose."
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