TORONTO - Premier Dalton McGuinty will unveil Ontario's new Liberal cabinet Tuesday, ending one of the most difficult jobs faced by any political leader -- deciding who gets a coveted seat at the cabinet table and who remains in the backbenches.

Liberal sources say Friday's surprise announcement that Finance Minister Greg Sorbara does not want to be reappointed to cabinet meant McGuinty would have to spend the weekend revising his cabinet plans, which he's been quietly working on in seclusion since the Oct. 10 vote.

Sorbara said he wants to spend more time with his family, which leaves a big hole for McGuinty to fill, but also means there's one less Liberal clamouring for a spot in cabinet, said party insiders.

Leaders have always had to take into consideration gender and geographic concerns when making up a cabinet -- striking a balance to ensure a good mix of men and women and that each area of Ontario is represented. But Greg Inwood, associate professor of politics at Ryerson University in Toronto, said ethnicity is now another issue to be considered.

"That's been a factor that's been becoming increasingly important over a period of years now in Ontario with the demographic changes and the move to a much more multicultural society,'' said Inwood.

"Interestingly enough, it's sort of supplanted religion, dare I say.''

In the Liberals' first term, McGuinty created a new Revenue Ministry so he could promote Michael Chan to cabinet after the government was criticized for not having a Chinese-Canadian in cabinet.

This time out, newly elected Margarett Best of Scarborough-Guildwood, a lawyer, is the only black member of the Liberal caucus, but there are many other more experienced men and women who did not make cabinet in the first term -- including other visible minorities such as Bas Balkissoon from Scarborourgh-Rouge River -- who may expect to be promoted this time.

McGuinty has not been seen publicly since the day after the election, but while resting at a cottage he has also been working on the makeup of his new cabinet, something Inwood said is always a difficult task because he must also consider factors such as loyalty to the leader, old political debts and which backbenchers are truly deserving of a promotion.

"It's quite a balancing act, and ironically enough, almost the lowest criteria on the whole sheet is merit or skill,'' said Inwood.

"Sometimes that gets shoved aside in favour of some of these other important considerations.''

Leaders prefer majority governments, but a big win like the Liberals had Oct. 10 can present another problem: too many elected members who want into cabinet and not enough chairs around the table, which makes it hard for a premier to keep everyone happy and can lead to unrest in the ranks.

But McGuinty effectively defused that problem in his first term by inviting backbenchers onto cabinet committees, involving them more in the decision-making process while at the same time making them subject to cabinet's oath of secrecy.

"That was unique in Ontario history,'' said Inwood. "I think that was a big step in terms of addressing the issue of what do you do with this large body of backbenchers whose only outlet is the weekly caucus meeting.''

McGuinty has 70 other Liberals in his new caucus, and he can't expand the cabinet much beyond the current 27 positions without leading to opposition charges that he's running an expensive, bloated government, so inevitably there will be some noses out of joint by those who are left out.

Liberals say in all likelihood McGuinty did have Sorbara pencilled in as finance minister again, so obviously there will be at least a couple of major changes as another senior minister is moved into finance, creating room for another more junior minister at the table.

Energy Minister Dwight Duncan is a possible replacement for Sorbara.

Duncan filled in as finance minister when Sorbara had to step down in 2005 because of a police investigation into a land deal involving his family business, and both men returned to their previous posts once Sorbara was cleared by the RCMP.

Prior to Sorbara's announcement Friday, few observers expected McGuinty would want to put a completely new face on the re-elected Liberal government by making major changes to the cabinet.

Most predicted he would stay the course with ministers who have performed well, eliminating the need for new ministers to get up to speed on complicated files.

There's still no indication that McGuinty will call the legislature back for a short session before the Christmas break, but the first order of business _ even before a throne speech to open the session -- will be the election of a new Speaker by members of all three parties.