Which leaders resign, like Jacinda Ardern? Often, the system decides

When Jacinda Ardern announced this week that she would step down as New Zealand’s prime minister, her decision caught the world by surprise. She called leading a country “the most privileged job anyone could ever have,” but said she would leave office by February.

It was particularly striking to see a leader voluntarily relinquish power at a moment when the world’s strongmen — and even some elected presidents — are clinging ferociously to theirs.

Jair Bolsonaro of Brazil, for instance, has disputed the election results that recently removed him from office, with some of his supporters storming the country’s legislature in an apparent mimicry of the United States’ own attempted insurrection in 2021.

Ardern framed her resignation as a personal decision based on no longer having “enough in the tank” to fulfil the responsibilities of being prime minister. Some supporters have also praised her move as embodying the democratic ideals on which she spoke passionately.

But what separates leaders who step down from those who do not often turns less on that leader’s ideology or personal life than on the simple nature of their political system.

In parliamentary systems such as New Zealand’s, it is the norm for leaders to step down when it is thought that doing so will best serve their party’s electoral prospects. Sometimes such a resignation is voluntary, and sometimes it comes amid quiet internal pressure from party members. Usually it is a mix of both.

Although Ardern has said she is stepping down for personal reasons, her party is facing its worst poll numbers in years and a national election in October.

Parties in parliamentary systems often nudge a leader to step down in such circumstances because they can elevate a new prime minister from within their ranks to win back voters before the next election. (In New Zealand, another member of Ardern’s Labour Party was nominated on Saturday to take over as prime minister.)

In such situations, the party’s incentive is to keep this process quiet, so as not to air internal divisions or project political weakness. This often creates the appearance of a graceful and voluntary resignation.

Angela Merkel, Germany’s longtime chancellor, stepped down voluntarily in 2021, also several months before national elections in which her party faced difficult poll numbers. She presented the choice as hers, preserving her political stature and her party’s show of unity. Her party carefully orchestrated Merkel’s handoff to a hand-picked successor. But the party nonetheless lost power in that year’s election.

In most parliamentary systems, prime ministers, unlike presidents, are elected by their party’s lawmakers. Those lawmakers typically also have the power to replace them at will, or at least to trigger votes that might remove them. As a result, power handoffs, even chaotic ones, are overwhelmingly likely to proceed peacefully.

“The vast majority of the stable democracies in the world today are parliamentary regimes, where executive power is generated by legislative majorities and depends on such majorities for survival,” Juan Linz, a prominent political scientist who died in 2013, once wrote. Presidential democracies, Linz and others have found, are unusually likely to collapse into coups or other violence.

Scholars have identified several reasons for this. One is that these systems are set up in a way that makes removing a leader far more difficult and gives it higher stakes, while also effectively discouraging leaders from stepping down voluntarily. The separation of legislative and executive branches means that a ruling party cannot simply change out an unpopular leader with a replacement as it can in parliamentary systems.

Rather, that party must use the legislature to pry the president from office via public impeachment proceedings. Even in the rare instances when this succeeds, it tends to open deep and damaging fissures within the president’s party, as well as grinding the government to a halt, which is why lawmakers rarely do it.

Even when they do, it can bring a constitutional crisis or worse. Peru, for instance, has been mired in chaos ever since its president dissolved the legislature in December to prevent it from holding an impeachment vote, which led to that president’s removal from office and weeks of nationwide unrest.

Presidents also know that resigning or declining to run for reelection would hurt their party’s prospects of holding power.

ARDERN FRAMED HER RESIGNATION AS A PERSONAL DECISION BASED ON NO LONGER HAVING ‘ENOUGH IN THE TANK’ TO FULFILL THE RESPONSIBILITIES OF BEING PRIME MINISTER