There are signs Stephen Harper is readying his long-awaited cabinet shuffle as a new poll suggests voter support for the Conservatives has slipped to its lowest level since 2006.

Sources say some cabinet ministers have been ordered to postpone international trips that would have taken place during the second week of July, fuelling expectations the Prime Minister may be using that time to meet with MPs as he ponders how to construct a new cabinet.

Separately, other sources say the Prime Minister's Office is telling some Conservative MPs and ministers to stay within 24 hours' travel time of Ottawa in early July.

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Next week, Foreign Affairs Minister John Baird is scheduled to be travelling abroad, and Mr. Harper will be devoting time to the Calgary Stampede, which begins July 5. The Prime Minister attends regularly as a Calgary MP, but this year in particular he must demonstrate solidarity with a city recovering from flooding.

One senior Conservative suggested that rather than announce a shuffle in the second week of July, Mr. Harper may use that time to talk to MPs and ministers about possible moves.

How big a shuffle the Prime Minister is planning will depend on whether he ousts Finance Minister Jim Flaherty and Defence Minister Peter MacKay from positions they've held for years. Mr. Flaherty has been in the job since the government took office, and Mr. MacKay has held his post since 2007.

Mr. Harper publicly signalled in mid-2012 that he planned a mid-2013 shuffle and called on ministers to tell him whether they planned to run in the next election– expected in 2015 – so he could take that into account when redesigning his team.

Mr. Flaherty, who has been battling a rare skin disorder with a strong drug regimen that caused weight gain, has made efforts to signal he wants to stay on in his post. He even told The Globe and Mail in early June that he thought he had another election in him.

Mr. MacKay, who has been an MP for 16 years, has also been the subject of speculation about whether he'd quit politics. His long-time chief of staff and a veteran communications aide have both left his office in recent days.

On Thursday, the Defence Minister said he has more to contribute. "Despite the speculation, I have no plans to leave federal politics. I've been in public service first as a Crown prosecutor and then elected office for over 20 years now, but feel I still have more to offer and more to do," he said.

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"The decisions of [my staff] to leave were for personal reasons and have no bearing on my future. Both will be surely missed, but I respect the fact that they stayed significantly longer than most in their posts."

Mr. MacKay said he loves being Defence Minister, but when asked whether he wants to remain there, he said, "The decision on cabinet posts is the sole purview of the PM."

New poll numbers released by Nanos Research show Conservative support among decided voters fell to 29.4 per cent in mid-June from 31.3 per cent in early April.

Pollster Nik Nanos said the numbers have been slowly eroding since the 2011 election. This has accelerated in the past few months amid the Senate expenses scandal that claimed Mr. Harper's chief of staff. Nanos poll tracking records Tory support levels as the lowest since before the 2006 election.

The Liberals under new Leader Justin Trudeau remain in the lead at 34.2 per cent, down from 35.4 per cent in April. The NDP are at 25.3 per cent, up from 23.6 per cent. The poll of 1,000 adults is considered accurate to within 3.5 percentage points 19 times out of 20.

"What the Conservatives have to watch out for is whether this turns into the new trend line. It's too early to tell, but the longer the Liberals lead the more difficult it is to change the trend line," Mr. Nanos said.