New Democratic Party Leader Dominic Cardy’s byelection run received a boost on Tuesday morning when he received an endorsement from a political rival.

NDP Leader Dominic Cardy said his party and the People's Alliance will work co-operatively in the future (CBC)

People’s Alliance of New Brunswick Leader Kris Austin announced his party would back Cardy in the June 25 byelection and not run a candidate.

Austin said his party, which was formed before the 2010 election, had candidates who were willing to put their name on the ballot in the upcoming byelection.

"But we realized that if we want to send a clear message that two provincial parties can co-operate for the good of the province, we have to prove it with our actions," Austin said in a statement.

"Politics as usual just does not work in the average New Brunswickers’ best interests anymore."

The PANB leader said the co-operation pact is in the best interests of Rothesay residents but also of the entire province.

"Sending an NDP MLA to Fredericton would be more beneficial to the public than running a People’s Alliance candidate and having the new parties draw votes from one another only to continue the trend of red and blue corruption," he said in a statement.

Kris Austin votes in the 2010 election. His party will back the NDP in the Rothesay byelection. (CBC)

The Progressive Conservatives have nominated Hugh John Flemming III to replace Margaret-Ann Blaney, who resigned last month to take a job as the president and chief executive officer of Efficiency New Brunswick.

Political parties have blasted Blaney’s appointment as patronage.

The Liberals will be picking their byelection candidate on Tuesday night.

Parties have until June 8 to nominate their candidates for the Rothesay byelection.

Cardy said Austin’s support shows there is a desire among the province’s smaller parties to work together to unseat the Liberals and Progressive Conservatives.

"I have talked with Kris before, about how every New Brunswicker who wants to change the political culture of the province needs to work together. When it comes to the fight against patronage I am proud to have the People’s Alliance on my side," he said in a statement.

The two parties also said in a statement they will work together in the future "when possible."

Third parties have been shut out of the legislative assembly in the 2006 and 2010 elections.

In 2010, the NDP, Green Party and the People's Alliance had a combined share of 16 per cent of the popular vote.

Austin finished third in the riding of Grand Lake-Gagetown in the 2010 election.