Voter fatigue with Canada's ruling Conservatives and signs of stress within the government are putting Prime Minister Stephen Harper under pressure to freshen up his team and policies as the telegenic son of Pierre Trudeau starts snapping at his heels.

Even though the election is 30 months away - in October 2015 - the next few months will be a critical time for Harper, given mounting evidence in opinion polls that the Conservatives risk losing power after what would be nearly a decade in office.

A different government would likely raise corporate taxes and step up environmental controls, with costs to the energy and mining firms that lead Canada's growth.

A string of polls in the last two months put support for the Conservatives between 29 and 32 percent, barely enough to keep them in power with an unstable minority government.

The party, in power since 2006, won a majority in the May 2011 election with 39.6 percent of the vote.

"I don't think you can underestimate probably the internal fatigue of the government," said pollster Nik Nanos of Nanos Research.

The likely Conservative response: A restating of priorities, including: a balanced budget, then tax cuts, and a cabinet reshuffle.

That would give Harper the chance to bring in new younger ministers, and bring more women into the cabinet. Harper said last year that he planned big cabinet changes in mid-2013, and an aide said the plan remained on track.

The biggest external political threat comes from the Liberals, who have governed Canada more than any other party, but who sank to a distant third with less than 19 percent of the vote in 2011, behind the left-leaning New Democrats (NDP).

The Liberals are banking on the possible re-emergence of Trudeaumania, the voter excitement of 1968 when Pierre Elliott Trudeau became Liberal prime minister on a wave of flower power.

Trudeau's son Justin is likely to be elected Liberal leader on April 14, and polls show that helping the party enormously.

A Forum Research poll this month said they would win 40 percent of votes with Trudeau in charge, and perhaps a majority of seats. An Ipsos Reid poll on Thursday also had Trudeau Liberals ahead of the Conservatives, but by just one point.

Karl Belanger, principal secretary to NDP leader Thomas Mulcair, brushed off the threat from its rivals on the left. "The Liberals will pick their seventh leader in nine years," he said. "We will let them sort themselves out, the NDP is focused on the Conservatives."

Conservative strategists play down the opinion polls, noting how far away the next election is. They acknowledge Trudeau's charisma, but stress his inexperience.

Trudeau has banked on presenting a message of hope, much like U.S. President Barack Obama, and has sought to make a virtue of the fact that in many areas he does not have detailed policies, insisting that he will first listen to Canadians.

KEEP THINGS CLEAN

The Conservatives wrested power from a scandal-hit Liberal administration in 2006 with a promise to clean up Ottawa. But now the Conservatives have accountability problems of their own.

Two ministers were forced to quit this year over ethics violations and Elections Canada has laid charges against a Conservative campaign worker in connection with fraudulent robocalls in the 2011 campaign. The Conservative Party says it ran a clean campaign and was not involved with the calls, and anybody responsible should be prosecuted to the full extent of the law.

In an unusual sign of open protest against Harper, some backbench Conservatives are grumbling about tight controls on what they can do or say in public, particularly on abortion, which is legal in Canada but opposed by some in Harper's party.

One anti-abortion Conservative, Stephen Woodworth, accused Harper's government of being "tyrannical" after party whips denied another lawmaker the opportunity to speak in Parliament about a proposal to condemn gender-selective abortion.

Harper's answer to his woes looks set to include the largest single cabinet shuffle since he took power. The timing is unclear, but he has said it will be in mid-2013.

"He will not be fiddling around at the edges or moving a few pieces around," a leading Conservative told Reuters.

A key question is whether Jim Flaherty will stay on as finance minister despite health problems. He has held his post from the moment Harper formed his government in 2006, and says he wants to stay until the budget is balanced in 2015.

Though he ran up record budget deficits in response to the recession, markets see Flaherty as an experienced hand determined to balance the budget without tax hikes.

Harper has until now kept his cabinet changes moderate, preferring to stick to tried-and-true ministers over new blood.

"If the Conservative end game is to be a governing party in the long term...then they're going to need something before the next election that puts some sort of newness on what the party has to offer," Nanos, the pollster, said.

After the shuffle he will lay out his priorities for the second half of his term, expected to include tax cuts (in time for the election), action on shortages of skilled labor that have bedeviled the natural resources sector, getting oil to markets and reaching free-trade agreements.

In the 2011 election, both the Liberals and the New Democrats, the biggest opposition party at present, campaigned on a promise of higher corporate taxes, either rolling back tax cuts brought in by the Conservatives or raising them further.

Both opposition parties have pledged to implement some sort of carbon-pricing scheme, whether a cap-and-trade system or a straight carbon tax, and both have opposed Conservative measures to limit the environmental assessments.

They would also be more cautious on oil pipelines, currently opposing the proposed Northern Gateway pipeline from Alberta to British Columbia, which would enable crude to be shipped to China. The Liberals back the Keystone XL line to take Canadian crude to refineries in the United States, but the NDP does not.