OTTAWA — The race for the leadership of the federal Conservatives will come down to old-fashioned organizational elbow grease as the various camps work to get out the vote at the Toronto convention hall on May 31.

The party says about 2,300 delegates have registered for the event with less than three weeks to go, and most of the leadership camps expect at least 2,500 voting delegates will be on hand to choose Joe Clark's successor.

But with roughly 4,000 party members potentially eligible to vote at the convention, the 1,500 who fail to show up could be kingmakers by default.

"This is a one-on-one business, mano-a-mano," said John Laschinger, the veteran political strategist heading up the campaign of Tory MP Peter MacKay, the leadership front-runner.

"If one person can't come, there are alternates we can move up. We're going through that process in various places."

Marjaleena Repo, a senior advisor on David Orchard's campaign, said the convention cattle call comes down to motivation.

"Somebody described Orchard supporters as walking over broken glass to get there," she said. "There's an element of truth in that."

MacKay, the 37-year-old son of a Mulroney-era cabinet minister, survived the first stage of the new two-stage leadership process with a healthy but by no means insurmountable lead in available delegates.

In all, 2,788 card-carrying party members were elected as delegates. As well, 1,200 past and present Conservative party officials are free to attend and vote.

Based on riding votes by the 45,000 party members, MacKay won 42 per cent of elected delegates.

His closest competitor was Orchard, a Tory outsider who ran previously for the leadership on a platform of environmentalism, nationalism and more restrictive trade rules. Orchard earned 25 per cent of delegates.

Calgary lawyer Jim Prentice was next with just under 15 per cent. Tory MP Scott Brison managed about 10 per cent, and fellow MP Andre Bachand less than four per cent.

Two other fringe candidates, Heward Grafftey and Craig Chandler, won a handful of delegates between them. Another four per cent were elected as undeclared delegates.

The neat, democratically elected delegate percentages become fuzzier the closer the convention looms.

There are several reasons.

One is as old as electioneering itself: getting out the vote.

Delegates can only vote if they get to Toronto for the convention, including paying registration fees that can run up to $600, plus travel and accommodation expenses. Many won't bother. The SARS scare also deterred delegates, especially the elderly, say organizers, while looming provincial election calls in New Brunswick, Newfoundland and Ontario could hobble many potential delegates.

Another wildcard is the ex-officio, or automatic, delegates. They include party executives, current and former Tory MPs and MLAs, senators, riding presidents, candidates in the last federal election and others - as many as 1,200 in all.

More than 400 have already registered and most campaign organizers anticipate 600 to 800 will attend. And while the elected delegates have no free vote on the first ballot (their designated vote is logged when they register), automatic delegates are free to vote as they wish.

Even the elected delegates aren't necessarily wedded to the candidate they must represent on the first ballot. Anomalies in the riding voting system mean some are slotted in enemy camps.

For instance Asad Wali, campaign spokesman for Brison, is attending as a MacKay delegate.

"This process is just nuts," said Wali, who argues MacKay's early lead in elected delegates could evaporate.

"Part of that is because they're paper members from paper ridings. They are people who were there to stack a meeting and fill up spots on the ballot."

MP Rick Borotsik, Tory party whip in the Commons and a Prentice backer, said the convention will really take flight after the first ballot, when all delegates will be free to vote their conscience.

"It opens up a whole interesting leadership race on the second ballot - and it will go to a second ballot," said the MP for Brandon, Man. "You can take that to the bank. There's no way that MacKay can do a first ballot (victory)."

More dispassionate observers agree the convention format leaves plenty of room for traditional horse-trading, but they still give MacKay the edge.

One reason, says political scientist Heather MacIvor of the University of Windsor, is the heavy influence of automatic delegates, who tend to vote for the establishment candidate. MacKay fits the bill.

Orchard is another factor.

If the party outsider can muster enough delegates in Toronto to give MacKay a scare on the first ballot, many Tories may rally around the safest bet, said David Docherty, chair of political science at Wilfrid Laurier University in Waterloo, Ont.

"My reading is there's more likely to be fear of a David Orchard win, in which case people move to MacKay - particularly among those 600 to 1,000 (automatic delegates) who really don't want Orchard there."