The astounding increase in NDP popularity makes this election harder than usual to predict.

But there are probably just three scenarios that will play out, regardless of which party takes the most seats in the next House of Commons.

Courtesy of Queen's University professor and parliamentary expert Ned Franks, here are the scenarios Canadians could see following May 2.

1. A majority government. If it's a Conservative majority, then Stephen Harper continues as prime minister.

He retains the title throughout the election in any event and it's actually up to him to resign if another party wins a larger number of seats on election night, which is what he said he would do in his interview with the CBC's Peter Mansbridge.

2. A minority government with an opposition party holding the most seats. If the NDP, Liberals or even the Bloc Québécois were to win the largest number of seats - but no majority - Harper could still face the House and try his luck.

"Even if the Tories win fewer seats than the Liberals or NDP, they are entitled to meet the House and face it in a vote of confidence," Franks said. "Prime ministers in Canada do not normally exercise this right."

But there was at least one famous instance of this taking place: Mackenzie King in 1925 when his party fell to second place in a minority Parliament, more than a dozen seats behind the Conservatives, but stayed on for some months anyway with the support of the Progressives.

3. A minority Conservative government. Harper could continue as prime minister, perhaps much as he has for the past five years by cajoling and/or coercing support issue by issue.

Still, he could lose a confidence vote soon into his term if the other parties gang up on him, something he has been warning about constantly throughout this campaign.

Would this gang-up be more or less likely to happen if the NDP turns out to be the second-place finisher? That is, would the Liberals want to make Jack Layton prime minister and so affirm their third-party status? We leave that to the analysts.

All we know for certain is that in this third scenario, a minority Conservative government would have to table a throne speech to lay out its priorities and a budget (the one in March was never passed), presumably within the next month or so.

Months and months

If a minority Conservative government were to lose either of those votes, or any confidence vote within, say, four to six months, Harper would have to resign. But he would have the option of asking Gov. Gen. David Johnston for another election.

Normally, the governor general is supposed to act on the "advice" of the prime minister. But in special circumstances like these, "the reserve powers of the Crown come into play," Franks points out.

"These reserve powers permit the governor general to reject Mr. Harper's advice if he requests a dissolution when he holds a minority of seats in the House of Commons and is defeated early in the session of the new Parliament."

At that point, the governor general would inquire whether another party leader could gain the confidence of the House and govern instead, with the support of one or more other parties. 

Franks suggests Johnston might well make the leaders commit to such an arrangement for 18 months to two years; indeed, commit to it in writing and make the agreement public.

Franks is basing these time limits - at least four to six months before Johnston would grant another election, and 18 to 24 months for an alternative government to work - on what Adrienne Clarkson wrote about her preparations in case Paul Martin's minority Liberal government fell back in 2004.

That was the year, incidentally, when Harper, Bloc Leader Gilles Duceppe and NDP Leader Jack Layton prepared a letter to remind Clarkson that she didn't necessarily need to grant an election if Martin lost a confidence vote in the House.

Overall, Franks says, "the governor general's first and most important duty is to ensure that there is a prime minister."

Three precedents

If we do wake up on May 3 with what the Brits call a hung Parliament and the Conservatives not in a commanding lead, then there are three precedents to keep in mind for when second-place finishers might step up and govern.

• The October 1925 federal election in which the (and scandal-plagued) Mackenzie King Liberals governed for another eight months until the Conservatives were given a brief shot and an election was called. (History buffs will know this as the infamous King-Byng affair.) 
• The May 2,1985 Ontario election (52 Conservatives, 48 Liberals and 25 NDP) after which Liberal David Peterson and then NDP leader Bob Rae agreed to a two-year "accord" (not a coalition) to put Peterson in the premier's chair.

Note: Negotiating the accord and defeating the ruling Conservatives on their throne speech took nearly two months to bring about.

• The May 6, 2010 British election, which resulted in the first minority parliament at Westminster in decades: 307 Conservatives, 257 Labour and 57 Liberal Democrats.

For four days, the three parties entered into separate but intense negotiations to determine who would support whom, the result being a formal coalition arrangement between the Conservatives and Liberal Democrats.

The deal was struck nine days after the election and Parliament reconvened a week after that, which was a long time for the Brits but incredibly short by Canadian standards.

For more information on coalition governments, click on the Coalition category at the top of this post and see how we've reality checked the issue throughout the campaign.