OTTAWA — One of Jack Layton's closest advisers is emerging as a surprise front-runner to pick up the torch from the fallen NDP leader.

Party president Brian Topp is receiving a lot of encouragement to join the impending race to succeed Layton, who died on Monday, insiders say.

Topp is one of the key architects of Layton's success and was among the last of Layton's tight-knit inner circle to speak with him before his death.

Montreal MP Thomas Mulcair, Layton's deputy leader, is widely considered the only other prospective candidate to have a serious shot at taking Layton's place.

Signs of leadership jockeying emerged Tuesday even as plans were drawn up for Layton's body to lie in state on Parliament Hill and Toronto's City Hall before a state funeral in Toronto on Saturday.

Layton's body will rest for visitation in the foyer outside the House of Commons, where the NDP leader used to joust daily with reporters.

The lying-in-state will be open to the public Wednesday from 12:30 p.m. to 8 p.m. ET, and Thursday from 9 a.m. to 1:30 p.m. ET.

The state funeral, normally accorded only to current and former prime ministers, current cabinet ministers and governors general, was offered by Prime Minister Stephen Harper out of respect for Layton's stature. The ceremony is set for Roy Thomson Hall.

Topp, meanwhile, declined to comment on his possible leadership aspirations.

"We lost Jack yesterday and his funeral is on Saturday," the bilingual Topp said in an interview. "It's not appropriate to talk about his successor this week."

Mulcair could not be reached for comment.

Layton himself broached the leadership issue in a death-bed letter to Canadians, released just hours after his death from cancer. Topp, along with Layton's wife, MP Olivia Chow, and his chief of staff, Anne McGrath, helped Layton craft the letter Saturday, just over a day before the leader passed away.

In it, Layton urged the party to choose a replacement as soon as possible in the new year, giving his successor almost four years before the next election to put his or her stamp on the party.

The party's federal council is expected to meet the first week of September to set the leadership process in motion. A leadership vote is likely in mid-January.

Given the short time frame, it's not surprising that New Democrats are already buzzing about potential contenders, despite their grief over Layton's untimely death.

Names of other prospective candidates are floating around, including former Manitoba premier Gary Doer, former Nova Scotia NDP leader and newly elected MP Robert Chisholm, and veteran MPs Libby Davies and Paul Dewar.

However, insiders say most of those would be handicapped by their lack of fluent French. Fluency in both official languages is widely accepted as a precondition for any leader, particularly since Layton's historic success in Quebec in the May 2 election. The party swept 59 of the province's 75 seats.

The fact more than half the NDP's 103 seats are from Quebec gives Mulcair a leg up entering a leadership race. Until the election, the one-time provincial Liberal cabinet minister was the NDP's lone standard-bearer in the province. He is credited with laying much of the groundwork for the party's breakthrough on May 2.

However, Mulcair is a mercurial, abrasive figure, who may find it hard to emulate Layton's folksy charm. Moreover, the party's leadership process could work against him.

Under the NDP's constitution, every member of the party will be able to vote for a new leader. The results are not weighted to give equal clout to ridings or regions.

Provinces where the party's membership is highest -- British Columbia, Ontario, Saskatchewan and Manitoba -- will have the biggest say in determining who succeeds Layton. Quebec, at the moment, has the fewest members and, therefore, the least influence.

Members of affiliated trade unions are also entitled to vote for the new leader, accounting for about 20 per cent of the ballots.

Topp has deep roots in the New Democratic Party, particularly in member-rich Ontario and the West, and in the labour movement.

Born and raised in Quebec, he is currently executive director of ACTRA Toronto. He's worked for the party for decades, serving as deputy chief of staff to former Saskatchewan NDP premier Roy Romanow during the 1990s. He co-ordinated the federal NDP's campaign war room in the 1997 and 2004 elections, and was national campaign director in 2006 and 2008.

He has been asked to direct the British Columbia provincial campaign, expected this fall.

Insiders won't say whether Layton personally encouraged Topp to consider running to succeed him. But in June, when Topp was acclaimed party president, Layton pronounced it "a great day for our party."

"Brian Topp is one of the most principled and hard-working people I know. He's been an integral part of our team for years and is just the person we need to bring us to the next level," Layton said at the time.