As NDP Leader Jack Layton announced he's facing his second bout of cancer in a year and a half, there are signs his party is rattled.

Layton said Monday he's taking time off to focus on treatment,  though he wouldn't say what kind of cancer he now has. 

The reluctance of NDP members of Parliament to talk about Layton after the announcement could be a reflection of how seriously the party takes the threat to his health and to the future of the party itself.

MPs and even an Ontario NDP MPP cancelled interviews, at the party's request, they said. One MP walked into CBC's Ottawa newsroom, got a phone call, and said he couldn't do the interview after all. Another cancelled a local radio interview scheduled for Tuesday.

About an hour after Layton's announcement, it was hard to get MPs on the phone.

NDP staff have been protective of Layton, gently taking on reporters for mentioning his cane in stories or using shots of him sweating due to the pain of standing on a bad hip.

They genuinely like Layton and are worried about his health. And they've been forced to brush off questions from reporters, both on and off-the-record, since he revealed his first diagnosis in February 2010.

Layton hosted the press gallery at his new home at the end of June, but spent most of it sitting at a table and letting journalists go to him. As it ended, he hobbled away on his cane, flanked by a staffer and his wife, MP Olivia Chow, looking older than 61.

Layton 'critical' to party

When Layton took over the party's leadership in 2003, it had 14 MPs in the House of Commons. On May 2, the NDP won 103 seats — and Official Opposition status.

He was the face of the party's recent election campaign. His leadership numbers had always been strong, but the party's popularity only caught up with his personal popularity in the last campaign. He's credited with the NDP's big gains in Quebec. Ian Capstick, a former NDP strategist and CBC panelist, says the advances are partly due to Layton's personal connection with Canadians.  

"He is critical to the success of the New Democrats. He's critical through his long-term vision for a modern political party that can sustain itself regardless of who's in charge."  

Capstick says Layton insisted on aggressive organizing and training volunteers, using modern polling practices and fundraising techniques. He says those things will remain even after Layton finishes as leader.

"These things stand as a testament to Jack Layton's leadership that most people don't see."

Longtime NDP MP Bill Blaikie, now a cabinet minister in Manitoba's NDP government, says it would be hard to overestimate Layton's importance to the party.

"Obviously he's a key person to the party and to the current status of the party, which is an unparalleled status for the NDP in Canadian politics," he said.

Rookie MP to lead party

Expecting to be on leave only until the House returns Sept. 19, Layton has recommended the party choose rookie MP Nycole Turmel as interim leader — passing over his two deputy leaders, Montreal MP Thomas Mulcair and Vancouver MP Libby Davies.

Party officials are stressing that Turmel is not inexperienced — she's been active in the NDP for 20 years and led one of Canada's biggest public sector unions before she ran in Hull-Aylmer, taking out longtime Liberal MP Marcel Proulx.

"Listen, nobody was born into these jobs, right? There's no graduate degrees in becoming a federal leader. Everybody is new until they're not new again," NDP president Brian Topp told host Evan Solomon on CBC's Power & Politics.

"Nycole Turmel is a senior, experienced and very effective politician. She's quite well-known in the province of Quebec and is about to be well-known across Canada," he added.

Layton's recommendation doesn't mean it's final. MPs will meet Wednesday and discuss the issue before making a recommendation to the federal council, which meets Thursday before making the final decision.

Talk almost immediately turned to why Layton would recommend Turmel over Mulcair or Davies.

Capstick says Turmel is someone who's proven she can run national organizations with multimillion dollar budgets. It's also important she be able to speak French in a caucus with 59 Quebec MPs.

But it also comes down to maintaining a delicate balance in the party.

"You've got two deputy leaders of the party. You can't just elevate one over the other. Jack's been able to strike a balance between the left of the party and the right, and the francophone and anglophone … Yeah, I wouldn't have upset that apple cart," Capstick said.

Topp says MPs can recommend another MP to the federal council if they choose.

But "I'd be very disappointed indeed, as all the party members would be if there was any kind of a power struggle when the leader's been so clear about how he'd like this matter to be dealt with," he said.

"One of the advantages of this approach is that you're appointing a caucus officer who was unanimously elected to her position [as chair] and you're not putting yourself in the position of asking the caucus and then the federal council to make a choice between two deputy leaders."

As of Monday night, the NDP homepage featured a photo of Turmel and the words "Meet the NDP caucus chair" and "experienced leadership." At the moment, she's the only MP other than Layton to have her face featured so prominently.

Layton expects to be back before Turmel will have to lead off question period or take on any of the parliamentary functions of a leader. But Turmel and the other new MPs of the 41st Parliament only had 15 sitting days, plus a day for the Speaker's election, before the House rose for the summer.

Turmel herself says it will be a tough time for the party until Layton returns.

"It will be a difficult period because Mr. Layton is a great leader," she told CBC Radio. "We have a strong team, starting with Mr. Mulcair and the group of people elected, even if they are not known to the majority of Canadians," she added.

"We want to make sure that Mr. Layton is OK, that his health is a priority."

'Don't let them tell you it can't be done'

On the day the House of Commons fell last March, NDP Leader Jack Layton stood with his cane in front of reporters, facing questions about his health.

He had returned to work from hip surgery just two weeks before. There was speculation it was linked to his prostate cancer, though he insisted he was feeling very well. And he handled it with typical humour.

"I had my stitches out yesterday, I expect to be rid of the walking assistance in a few weeks. I'm not sure what other details you want. I could undress right here before you, but I don't think that would be in the interest of Canadian politics or good television," he said, smiling.

Anyone, including spokespeople from other parties, who talked to the media about Layton Monday spoke about his focus and determination. They could have referred back to his theme of optimism before the election, one the party stuck with as it fought to convince voters it was ready for Official Opposition.

As he said throughout that campaign, "Don't let them tell you it can't be done."