Jean Charest was probably in — and then he was definitely out. Rona Ambrose was thinking about it — then she stopped. Peter MacKay is in and, by all accounts, still is. Pierre Poilievre was going to throw his hat into the ring, too. Until he wasn't.Yes, the Conservative leadership race we all expected has not quite materialized.Poilievre's surprise announcement on Thursday that he would not mount a bid for the leadership leaves the contours of this campaign ill-defined. The Ontario MP was widely considered to be the main competition for MacKay, the former cabinet minister and last leader of the federal Progressive Conservative Party.Poilievre did have a path to victory. As the only major candidate with roots in Western Canada — he was born and raised in Alberta — Poilievre had the potential to take the lane as the candidate of the West, where the party's caucus, membership and donor base are disproportionately located.Watch: What high-profile exits mean for the Conservative leadership race He had the chops to be a player in Quebec. Only a few days ago, he was on Radio-Canada and, by speaking decent French and expressing views on social conservative issues that were in line with mainstream opinion in the province, dispelled the two biggest concerns Quebec Conservatives had with Andrew Scheer's election performance.Combined with his track record as a partisan pitbull for Stephen Harper, he appeared to be the most likely recipient of votes from members opposed to MacKay — and to any swing back to the old PC wing of the party that took a back seat to the Reformers after the 2003 merger.An opening for O'TooleWith MacKay and Poilievre on the ballot, there didn't appear to be much room for Ontario MP Erin O'Toole, who finished third in the 2017 leadership race and will be mounting a second attempt. He ran his last campaign as a consensus candidate in the centre of the party, gaining the support of members who voted for moderates like Lisa Raitt and Michael Chong and disproportionately ranked O'Toole as their second choice.MacKay is well-positioned to occupy this lane. He has already received the endorsement of three MPs who backed O'Toole in 2017. Even MacKay's regional base overlaps with O'Toole, who had his best results in New Brunswick, Prince Edward Island and Nova Scotia.Atlantic Canada is likely to be MacKay's fiefdom: he represented a riding in Nova Scotia for nearly two decades, the same seat his father Elmer occupied for even longer, and he has the backing of Tim Houston, the provincial PC leader in Nova Scotia.But there is now an opportunity for O'Toole to take up the space left vacant by Poilievre.That will be no easy task. But by the process of elimination, O'Toole has the best shot at it. Instead of being squeezed out between MacKay and Poilievre, O'Toole merely has to position himself to the right of MacKay as the only acceptable option for members looking for an alternative.An opening for someone elseOther names probably will join MacKay and O'Toole on the ballot. Ontario MPs Marilyn Gladu and Derek Sloan have indicated they want to run. The 12th place finisher in 2017, businessman Rick Peterson, says he will take another kick at the can, as have a number of former staffers and failed election candidates.But until these people meet the Conservative Party's demanding qualification requirements, or give some tangible evidence that they are serious contenders, this looks like a two-horse race.It's a race with no frontrunner from Quebec and nobody from Western Canada. Only a single candidate has a name that a majority of Canadians can recognize: Peter MacKay.So, will this be it?Justin Trudeau's Liberals are in their second term and were reduced to a minority government only last fall. The Conservatives continue to run roughly even with the Liberals in national polls. The next leader of the Conservative Party has a good shot of becoming the next prime minister — certainly a better shot than appeared to be the case in 2017.Charest's decision on Tuesday left Quebec up for grabs. On Wednesday, Ambrose left the field wide open in Western Canada. Poilievre relinquished his contender status on Thursday, along with all the organizers and donors his candidacy would have taken off the table for other candidates.This race looks a lot different than it did on Monday. Anyone who had ruled out a bid at the beginning of the week might want to take the weekend to think it over again.