The ghost of elections past is coming back to haunt Stephen Harper.

The Liberals are pointing out that when Harper campaigned against Liberal prime minister Paul Martin in 2005, he promised he would defend seniors' public pensions.

In a speech to seniors in Guelph on December 9, 2005, Harper said seniors, like his mother, had worked for years to pay into the public pension system and that they expected it to be there for them.

“My government will fully preserve the Old Age Security (OAS), the Guaranteed Income Supplement and the Canada Pension Plan, and all projected future increases to these programs. And we will build on those commitments," Harper promised before winning the election in 2006. You can see video from the speech below.

Harper first hinted at changes to OAS in his speech to the World Economic Forum in Davos last month and later confirmed that the Tories are considering raising the eligibility age for OAS.

The media has widely speculated that the increase will be from age 65 to 67. Keeping seniors in the workforce longer would lighten the burden on OAS.

Harper has stressed, however, that any changes would not affect those who are currently in, or approaching, retirement.

The Tory telegraphing on public pension changes has triggered protest from opposition parties and retirees. On Thursday, seniors and labour activists staged sit-ins at the offices of 24 MPs to protest changes to OAS.

Finance Minister Jim Flaherty has argued that OAS changes are necessary to protect the fiscal health of the government moving forward. But he has been contradicted by budget watchdog Kevin Page, who earlier this week denied that there is a public pensions crisis. Flaherty characterized Page as "unbelievable, unreliable, incredible" in response to the Parliamentary Budget Officer's comments.

It just goes to show how much a country's politics can change after a major financial crisis. In December 2005, the Tories were running campaign ads, like the one below, promising "to protect public pensions." Today, they're arguing that pension changes are necessary to protect the nation's balance sheet.

The good news is that while OAS may be headed for major change, the Canada Pension Plan (CPP) appears to be in good shape. Harper recently described CPP as "actuarially sound.”

If you want to learn more about the differences between OAS and CPP, check out the slideshow below.

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