OTTAWA - Former Saskatchewan premier Lorne Calvert is endorsing Brian Topp for leader of the federal NDP.

Calvert says he believes Topp is the contender best able to hang onto the NDP's record gains in Quebec and build support in the rest of the country.

Topp was born, raised and cut his political teeth in Quebec, although he now resides in Toronto.

But he also has deep roots in the West, particularly in Saskatchewan where he served as deputy chief of staff to Calvert's predecessor, Roy Romanow.

Romanow is also backing Topp, who has racked up an impressive roster of endorsements from party luminaries, including former national leader Ed Broadbent.

Topp, a longtime backroom strategist, is one of eight candidates vying to fill the shoes of Jack Layton, who died in August after leading the NDP to a historic finish in last May's federal election.

New Democrats picked up a record 103 seats, vaulting into official Opposition status thanks largely to a surge of support in Quebec, which delivered 59 seats to the party.

Calvert says Topp is the one who can make the next crucial step for the party.

"Brian has the national experience necessary to lead our party and form a national government," Calvert says in the text of remarks to be made in Saskatoon.

"Brian knows how to win in Quebec and that is an asset absolutely necessary in our next leader. But winning in Quebec is not enough to get the job done. We must also win here in Saskatchewan and across the country.

"Brian can do that too."

Recent polls have suggested NDP support in Quebec has begun to slip away and that has injected an urgent note at the mid-point of the seven-month leadership contest, which culminates with a vote by all party members on March 24.

Montreal MP Thomas Mulcair is widely thought to be best poised to capitalize on New Democrats' preoccupation with holding on to their newfound Quebec base. The former provincial Liberal cabinet minister is well known in the province and is the only contender who currently represents a Quebec riding.

However, the fluently bilingual Topp is trying to present himself as a more well-rounded contender who can appeal to voters in both Quebec and the rest of the country.

Calvert says his choice was also influenced by Topp's integrity and his "courage" in advocating tax increases for the wealthy in order to pay for programs to boost the economy and opportunities for low and middle-income Canadians.

"While most leaders will shy away from the discussion about the need to rebalance our tax system, Brian has tackled it head on because Brian understands that if we are going to govern well we have to be honest about how we are going to pay for our priorities," Calvert says.

"Brian Topp is a man of integrity. Brian's convictions are not convictions of convenience. They are deeply held."

Topp, a longtime senior backroom strategist, has been criticized in some quarters for never having sought elected office. But Calvert argues that the best politicians are also good strategists.

"We need a good strategist to lead our party. Brian's ability for strategic thinking is a huge asset, particularly in taking on the current prime minister (Stephen Harper), who is not a bad strategic thinker himself."