OTTAWA - Prime Minister Stephen Harper is taking his third stab in four years at bringing democracy to Canada's unelected Senate.

But his latest attempt appears to be somewhat more conciliatory toward provincial governments, several of which strenuously objected to past attempts to reform the upper chamber without their formal constitutional approval.

The new bill, introduced Tuesday in the Senate, sets out a voluntary framework for provinces to begin electing Senate nominees.

Harper would retain his power to appoint senators but is committing to consider the names of nominees selected in provinces that choose to hold elections.

The voluntary framework is based on Alberta's Senate election model, which has resulted in the appointment of two democratically selected senators: Stan Waters in 1990 and Bert Brown in 2007.

The Harper government's two past attempts to democratize the Senate were more direct. They proposed creation of a national process, coinciding with either federal or provincial elections, to consult voters on who should be appointed to the Senate.

Because the prime minister would technically still appoint senators, the government argued that no formal constitutional amendment was necessary.

However, four provinces -- including Quebec and Ontario --maintained an amendment, approved by at least seven provinces with 50 per cent of the population, was needed. Quebec went so far as to threaten court action to stop Harper from proceeding unilaterally.

The new approach essentially codifies in law the status quo. Provinces are encouraged to set up Senate election processes but are not compelled to do so.

So far, Alberta is the only province to ever hold Senate elections. British Columbia, Saskatchewan and Manitoba have shown some interest but haven't yet followed through.

Earlier this month, the Harper government reintroduced legislation to set terms limits of eight years on senators.

Currently senators may serve up to 45 years, until age 75.