To a great many patriotic Canadians, it's an act bordering on treason, so they have a hard time understanding how so many Quebeckers do it.
Election after election, around 1.5 million Quebec voters cast ballots for the Bloc Québécois knowing its stated aim of turning the province into a country.
So just how easy is it for those 1.5 million people to change their minds?
The Bloc's total vote has swung some 25 per cent in its 20-year history, from a high in 1993 to a low in 2008, with several peaks and valleys in between.
There's still room for swing, recent polls have showed emphatically. The Bloc may be headed for an historically poor showing.
The list of motivations for many Bloc voters is actually much longer than the quest for Quebec independence.
Somewhere around 30 per cent of Quebec voters are committed separatists who won't budge easily, according to pollster Christian Bourque. But another 20 or 25 per cent are that amorphous gang known as Quebec nationalists. These are the people who moved in big numbers to the Bloc to protest the defeat of the Meech Lake constitutional accord in 1993 and again in 2004 to protest the breaking sponsorship scandal. To a lesser extent, the pattern was repeated in 2008 when minor Conservative cuts to cultural programs were blown up into an assault of the arts in Quebec.
The big swath of Quebec nationalists care deeply about protecting and promoting French language and Quebec culture, but aren't nearly as committed to creating a country. So when they feel secure about language, and when they're not enraged at some federal insult, they go shopping based on the usual Canadian criteria including leadership and party platform.
That's why the Bloc vote flagged in 2000 and appears set to do so again in 2011.
When voters across Canada are asked for their second choice, the NDP comes up most often. Long before this election campaign, this was also true for many Quebeckers.
Going into this election, the NDP has taken the side of Quebec nationalists on a number of issues, supporting bilingual Supreme Court judges and the imposition of French on federally regulated workplaces in Quebec.
With nationalist angles covered, some Bloc progressives are taking a liking to NDP Leader Jack Layton.
This leaves Bloc Leader Gilles Duceppe "blowing on the coals, but not creating any fire," Mr. Bourque said. "They'll come back when there's some outrage, but there's nothing there right now."
None of this means the Bloc is about to be abandoned. Even if the party's support sinks to an historic low, Mr. Duceppe is likely to win 30 per cent of Quebec votes and half of Quebec's 75 seats. Because in places where Mr. Duceppe has the most support, those voters are very committed.
Editor's note: The NDP has not taken a position endorsing the extension of French-language instruction in the Quebec educational system. The article has been corrected.