As Canada's political leaders head into Tuesday's debate, the Conservatives still hold a single-digit lead over the Liberals, according to the latest Nanos Research daily tracking poll.

Conducted exclusively for CP24, CTV and the Globe and Mail, the poll finds the Tories with 39 per cent of support of decided voters.

In second place, the Liberals have 31 per cent, followed by the NDP with nearly 17 per cent. Eight per cent of Canadians say they support the Bloc Quebecois, while four per cent say they support the Green Party.

Nanos says 990 people were polled between Saturday and Monday.

The poll is considered accurate to within 3.1 per cent, 19 times out of 20.

All but one of the party leaders is participating in Tuesday's debate. Green Party leader Elizabeth May is the odd person out.

The Broadcasting Consortium didn't invite May to the debate because the Greens don't hold a seat in the House of Commons.