Expect a frailer government to emerge from Canada’s election. Here’s why.

Canada looks poised to have a weaker, more unstable government after Monday’s election.

It’s a scenario in which the governing party can't control the House of Commons alone. It will need help from other parties not just to pass bills but also merely to survive as other parties can band together to force a new election at virtually any moment.

Think of it as divided government in Washington, but with a dramatic twist: Opposition members can topple the executive branch and prompt a new election with one simple majority vote.

It’s known in the British parliamentary tradition as a minority government, and it’s actually quite common. One-third of Canadian governments have been minorities in the last 30 years.

A party trying to govern with a minority in the House of Commons can either cooperate with smaller parties to pass bills or browbeat them, essentially daring the weaker party to trigger an election.

These unstable parliaments tend to last about two years but can actually be quite productive amid the chaos. One particularly active series of minority parliaments in the 1960s introduced old-age pensions, a version of Medicare, the precursor to the current Canada-U.S. free trade agreement and the modern Canadian flag.

One of Canada’s best-known experts on the parliamentary system, Philippe Lagassé, says minority governments can keep going because few politicians have an appetite for another election. Parties are usually too cash-strapped to campaign again, and losing parties are often too distracted by their own internal nomination fights.

“It creates a real incentive to keep this thing going for a while,” said Lagassé, a professor at Carleton University‘s Paterson School in Ottawa.

As POLITICO outlined, there are five possible scenarios that could emerge out of the election, but some form of minority government seems most likely. The latest polls indicate that neither the Liberal Party nor the Conservative Party will win the 170 votes in Monday’s election to hold the majority outright.

If Justin Trudeau and the Liberals end up with a minority, they could strike a pact with the left-wing New Democratic Party. In such an alliance, the NDP might demand more expensive, single-payer universal prescription drug coverage in exchange for a promise to keep Trudeau in office.

“I can certainly imagine the Liberals and NDP doing [a deal],” said David Moscrop, a political theorist at the University of Ottawa. “I think there would be some pressure to sign an agreement.”

Trudeau may even be able to maneuver into a minority government without winning the most seats. He could choose not to resign and team up with party No. 3 to form a majority — although it would be unconventional, and certainly controversial, if Trudeau and the NDP tried such a move. Trudeau himself once disparaged the idea of a losers’ coalition.

A far more conventional approach would see the party with the most seats trying to govern alone with no formal ally.

The minority party could seek to cut deals on a case-by-case basis, passing bills with the help of different parties. For example, Trudeau might seek NDP support on one of his main campaign promises, a prescription drug bill. He could then get the Conservatives’ votes to ratify the new U.S.-Mexico-Canada Agreement.

If Andrew Scheer and the Conservatives take over, they’re expected to take the go-it-alone route. They have no natural ally in Parliament, especially on an issue they’ve made central in their campaign: undoing Trudeau’s carbon tax and climate policies and encouraging oil-and-gas development.

But many of the Conservative Party’s other campaign promises could easily find support in Parliament — such as stricter data privacy rules for tech companies and targeted tax policies aimed at families like tax credits for sports equipment.

Either the Conservatives or Liberals could also govern in the minority with a confrontational approach.

The smaller parties are sometimes so desperate to avoid an election that they’ll accept embarrassing indignities and still keep the government afloat.

Take the last Conservative prime minister, Stephen Harper, who ran two minority governments. He regularly browbeat his opponents into passing his agenda, because they were more afraid of an election than he was.

A very unlikely, but not unheard of, result is a formal coalition government, in which different parties share seats in the executive branch.

Though common in nations governed by parliamentary systems, a formal coalition hasn’t been in place in Canada in over 100 years. The last time was during World War I, when members of Parliament who favored the draft banded together to form their own Cabinet.

In such a case, the smaller party, likely the NDP, might get some seats at the Cabinet and gain serious influence over the daily government operations. It’s what happened in the U.K. a few years ago, when the Conservatives and Liberal Democrats teamed up to form one government.

A basic principle of what’s called the Westminster system is that members of the executive branch remain united; any disagreements that might occur around the Cabinet table are kept secret.

Yet these parties know that in the not-too-distant future, they’ll be bashing each other again in another election and arguing about the government’s track record.

“It gets really messy in the Canadian system just because we’re not used to it,” Lagassé said.

“In a county like Canada, where governments tend to be very secretive and don’t disclose a lot of information and guard their secrets very aggressively, to suddenly have another party that you’re continually competing with, in the room with you, making decisions, is something we tend to not do,” Lagassé said. “It doesn’t mean it can’t be done. It’s just much more complicated.”

Minority governments fall in one of four ways, Lagassé said.

The first test is the throne speech, somewhat like the State of the Union address in the United States, that opens the new Parliament.

If it’s defeated in a vote so soon, another party might try forming a government to avoid an immediate election.

Another way to lose power is if the minority government loses a vote on spending money. A government can also collapse in a vote on a motion declaring non-confidence. Or it could fail if the government declares something a matter of confidence and loses the vote on it.

Trudeau’s father, Pierre, led one type of minority government and defeated another type. When he was in opposition, he had announced plans to retire before his rivals tried to govern alone — and it backfired.

Having just arrived in office and facing a weakened Liberal Party organizing to replace Pierre Trudeau, the Conservatives in 1979 tried ramming through a budget bill and assumed it would pass. It failed.

They were toppled after just nine months. Trudeau came out of retirement, won a fourth term in office and capped his career by overhauling the Canadian constitution.

But it was another, earlier episode that could prove eerily similar to the fate awaiting his son on Monday. Pierre Trudeau’s towering first-term popularity had collapsed. After a suspenseful election night, he scraped along, barely clinging to power.

Pierre Trudeau got help from the NDP for two years, from 1972 to 1974.

Their alliance crumbled after two years. Trudeau correctly surmised he could win another election and shrugged off the NDP’s demands in a budget bill.

The NDP’s leader, David Lewis, called his erstwhile ally arrogant and brought Trudeau down.

“He thought we were frightened about an election,“ Lewis said. “ He was crazy. We’re not.” Lewis promised a campaign for lower living costs against his friend-turned-rival.

The episode exemplifies the inherent instability of life with minority governments: Within two years or so, even the friendliest alliance can end in acrimony and a new election.