[Editor's note: This is the latest of a new feature on The Tyee through election day: Charting the Votes. In charts and prose, veteran political analyst Will McMartin breaks down the important factors in key B.C. races.]

Elizabeth May, leader of the Green Party, does not have a seat in the House of Commons. She needs one, of course, if the Greens are to be a serious factor in federal politics.

Yet for reasons best known only to herself, May opted to run in the current federal general election in the long-time Tory stronghold of Central Nova.

For 36 of the last 40 years, Central Nova -- one of 11 federal electoral districts in Nova Scotia -- has been held by either the Conservatives or the Progressive Conservatives. And for nearly all that time, a MacKay has been its member of Parliament.

Peter MacKay's deep roots in riding

Central Nova currently is represented by Peter MacKay, a high-profile member of Prime Minister Stephen Harper's Conservative government. He initially headed the Department of Foreign Affairs, and now is minister of national defence.

MacKay has been victorious in Central Nova in each of the last four general elections, topping the polls in 1997, 2000, 2004 and 2006. (The riding was called Central Nova from 1968 through to 1997, then became known as Pictou-Antigonish-Guysborough, and reverted back to Central Nova in 2004.)

Elmer MacKay, Peter's father, first won the riding in a 1971 by-election. He was re-elected in 1972, 1974, 1979 and 1980, but then resigned in 1983 to make room for Brian Mulroney, the then-new Progressive Conservative leader who did not have a Commons seat.

The elder MacKay regained the riding in 1984 when Mulroney returned to his home province of Quebec, and then held it again in 1988. In appreciation, Prime Minister Mulroney named him to a succession of cabinet posts, including solicitor general, national revenue and public works.

The sole occasion over the last four decades when Central Nova was won by someone other than a Tory occurred in 1993, when the once-mighty Progressive Conservatives were reduced to just two Commons seats. Elmer MacKay did not stand for re-election in that contest, opting instead to retire after a 21-year career as the riding's MP. His successor was Roseanne Skoke, a Liberal, who served a single term.

Peter MacKay then ascended to the family seat. Now 43 years of age, he has lived in Central Nova for nearly his entire life.

Third time the charm for May?

In contrast, Elizabeth May, 54, is a newcomer to the riding. Born in Connecticut, May was 18 years old when her family relocated to Nova Scotia's Cape Breton Island -- which is next-door to Central Nova -- in 1972. She graduated from Dalhousie Law School in 1983 and moved to Ottawa two years later. (MacKay also has a Dalhousie law degree, which he obtained in 1990.)

May worked as an environmental policy advisor in the Mulroney government for a couple of years, and in 1989 became the founding executive director of the Sierra Club of Canada. She held that post until 2006, leaving to become leader of the Green Party.

This is May's third attempt to win a parliamentary seat. She ran in Cape Breton in 1980, finishing fifth while representing a tiny fringe party, and then contested a byelection in London North Centre in 2006 as Green leader. She finished second in the latter contest.

Will Dion deal pay off?

Does May have any hope of victory on Oct. 14? There are at least two reasons to suggest that the Green leader could win the party's first-ever seat in Canada's parliament, although such a result remains a decided long shot.

First, May no doubt has elevated her personal profile in the riding as a consequence of participating in the televised leaders' debates on Oct. 1 and 2. Some Central Nova voters may decide she deserves their ballots on the basis of her performance, or her status as a national party leader.

Second, thanks to a controversial backroom deal with Liberal leader Stephane Dion, the Grits will not field a candidate in Central Nova. (The Greens similarly have pledged not to run a candidate against Dion in his Quebec riding of Saint-Laurent--Cartierville.)

May, therefore, may be able to reap putative Liberal votes in addition to historic Green support -- as small as the latter may be. The Greens did not run a candidate in the riding in either 1997 or 2000, and then got just 1015 votes in 2004, and a minuscule 671 ballots in 2006.

Still, that combination of Green-Liberal support gets May to about 13,000 votes at most -- well short of the 17,000 or so that Peter MacKay has averaged over the last four elections.

NDP rising in Central Nova

A major factor to consider is that recent elections in Central Nova have seen rising support for the New Democratic Party. After pulling fewer than 4,500 votes in 2000, the NDP obtained nearly 10,500 ballots in 2004, and then climbed to almost 14,000 in 2006.

Indeed, in the last two contests, the New Democrats got more votes in Central Nova than did the Grits. (It must be said that much of the growth in NDP support over those two elections was due to an extraordinarily popular candidate, Alexis MacDonald, who, nonetheless, could not defeat MacKay. She moved to Halifax so as to succeed the retiring former New Democratic Party leader, Alexa McDonough, but was unable to win the party nomination in that city.)

The challenge facing Elizabeth May is straight-forward. To upset Peter MacKay and win a seat in the House of Commons, she must retain the backing of all those residents who previously voted for either the Liberals or the Greens, and she must win over at least 6,000 or so former NDP supporters. It's a tall assignment.