Quebec MP Thomas Mulcair said Tuesday he is getting a lot of encouragement to run for the NDP leadership but hasn't made a decision.

He was not alone in his public musings about a leadership run, a number of other MPs confirmed they are taking it under consideration, including Pat Martin. Speaking to reporters in Montreal, the NDP's deputy leader said the support is not only coming from within Quebec, but from across the country.

"I have received a lot of encouragement, not only in Quebec where of course our base is very strong, but across Canada to consider running and that’s where we are – it’s something that I’m considering. I’m giving it deep thought with a lot of close friends, and indeed my family," Mulcair said in advance of a speech at McGill University's law school. "These are not easy decisions, the decisions involve a process and in the next weeks we’ll be able to announce something definitive."

Tuesday was the first time Mulcair had commented publicly on the leadership contest that is now being organized in the wake of NDP leader Jack Layton's death last Monday. A state funeral was held for him on Saturday in Toronto and while MPs say they are grappling with the loss of their leader, they are turning their attention to their party's future.

Mulcair said he's still in "deep mourning" over the loss of a very good friend and he shared  his memories of how Layton recruited him to run in Montreal's Outremont riding, where he won the longtime Liberal seat in 2007. Mulcair spoke about how far the NDP has come in Quebec and credited Layton for his vision and work in laying a foundation in Quebec and building upon it over the last five years.

"Whoever winds up being a candidate in this we have to seek one goal: a very good campaign, a clean campaign, a campaign of ideas, where the party can move forward and go to the next step, which is to form an NDP government," said Mulcair.

Speculation on who would try to be Layton's successor began almost immediately after Layton's death and is ramping up now that work is getting underway to organize a leadership convention. Quebec MP Nycole Turmel is acting as interim leader until a permanent one is chosen.

Mulcair, who was the only NDP MP in Quebec prior to the May 2 election when the NDP captured 59 seats in the province, has a high profile there and is bilingual. He was a former environment minister under Quebec Liberal Premier Jean Charest before jumping to the NDP.

So far, none of the NDP's 102 MPs have solidly declared they are running for the leadership. Some have ruled it out, while others say they are considering it.

Growing list of MPs considering leadership

Another Quebec MP, Francoise Boivin, is giving it some thought, according to her parliamentary assistant, Alexandre Gingras. He said Tuesday the Gatineau MP is waiting to see what rules are established by the party to govern the race before deciding whether to throw her hat in the ring.

Gingras said Boivin has already made one thing clear: that the next leader should be "perfectly bilingual."

If the party agrees with her and makes that a requirement, it would rule out a number of possible contenders from within the caucus whose French is not good enough.

Robert Chisholm, a new MP from Nova Scotia, would be among them. He told CBC News Tuesday that he is considering a run at the leadership and is currently doing French immersion training. A bilingualism requirement would rule out a number of willing and able people, he said, and he wants the race to be an "inclusive one."

Whether he will be part of it or not, he hasn't decided, but Chisholm confirmed he's weighing his options.

"It’s early days. I’m still trying to digest everything that’s happened in the last week as I’m sure everybody else is," said Chisholm. "I’d be lying if I said I wasn’t thinking about it."

The former provincial NDP leader in Nova Scotia and MLA for 12 years acknowledged his profile outside of his province is low, a challenge that other candidates would also have to overcome, he said.

He said that's why it's important that the campaign period is long enough to give the candidates time introduce themselves to NDP MPs and Canadians who want to join the party so they can vote for its new leader.

"We need time to get out and talk," he said.

Layton made it clear in a letter written before he died that his idea was for a leadership convention to be held as early as possible in 2012. Party officials say they will try and honour that wish, but a time and location are yet to be determined.

Chisholm said January might be too soon.

British Columbia MP Peter Julian is also on the list of MPs considering running for the leadership.

"I’m certainly hearing from some people and talking to some people, asking their advice," Julian told CBC News. "So I guess you could say I’m leaving the door open right now."

Also leaving the door open is Halifax MP Megan Leslie. She told CBC News that she hasn't ruled it out but is taking her time to consider her options. "It’s all happened very fast, and I owe it to myself and to the membership to consider it, but to also take the time to do so properly," said Leslie.

Martin would be "unity candidate"

In an interview with Evan Solomon on Power & Politics Tuesday, Winnipeg MP Pat Martin said he's also keeping the door open and wants to see a candidate in the race who is willing to co-operate with the Liberals.

Martin said he's always been open about advocating for what he calls a "recipe" for defeating Prime Minister Stephen Harper's Conservative government: "formal co-operation with the Liberal party for the next election."

"That’s what I’m going to be looking for in the leadership race. I will support the candidate that advocates and even promotes a formal co-operation with the Liberals for the next federal election and if I don’t hear any candidate saying that, then I will throw my hat in the ring and I’ll be the unity candidate," Martin said.

He said he thinks the NDP could probably defeat the Conservatives alone in the next election but with the Liberals their defeat would be guaranteed. He didn't specifically call for a merger of the two parties, saying he didn't want to propose a prescribed format for co-operation.

"United we stand, divided we fall," he said, calling for "petty bickering" to be put aside.

The NDP's federal council is in the process of reviewing the rules and regulations and they should be made known before MPs head to Quebec City for their summer policy retreat on Sept.13.

The NDP's chief party whip, Chris Charlton, said she is not running for leader and that she doesn't expect the competition to disrupt the strong sense of unity now being felt by the caucus.

"First and foremost, I think it's important that we continue to move forward as a united caucus. I'm confident that this leadership race is not going to be divisive, that whoever the candidates end up being will honour Jack's legacy of moving forward with a really strong team," said Charlton.

Gary Doer, the former NDP premier of Manitoba, has ruled out changing jobs. Currently Canada's ambassador to the United States, Doer told CBC News he is proud to be doing that job and is saying "no" when asked if he is interested in the NDP leadership.