Has a party that won an election ever lost its leader in the process?
In a Parliamentary democracy, general elections appoint constituency representatives. Most such appointees are members of parties with internally determined leaders. One or more parties then form a government, with one of these party leaders the head of government.
However, it's theoretically possible that a party that enters or stays in government due to its electoral performance has to change leader, due to that individual losing their seat. (Party leaders typically come from safe seats to prevent this.)
Has this ever actually happened? I'd be interested if this happened in the UK, or failing that in any nation with a Westminster system.
One thing to note is that the system of clearly designated party leaders, all of whom have seats in the Commons is relatively modern in the UK (at least compared to the age of the parliament). The government was last lead from the Lords by the Marquess of Salisbury in 1902.
Your question assumes district based elections - maybe it should be tagged as such (but which tag should be used? Maybe tag it "UK"). When using proportional voting, the first on the list - the leader - will be elected.
@Sjoerd It could also use Single Transferable Voting (STV). That doesn't have districts, but a party leader is not guaranteed to win like in a party list system.
@origimbo Lord Home was technically Prime Minister while in the House of Lords as well. He resigned his peerage and moved to the House of Commons *after* being chosen as Prime Minister (1963-1964).
Actually, in many parliamentary democracies, MP do *not* represent constituencies.
@J.G. Yes, Israel has pure PR at the national level. You're elected to represent the country as a whole (not only formally but also practically). If you are familiar with multi-seat constituencies like those in Ireland, you can think of this as one giant constituency covering the whole country. Another example would be the Netherlands, although it does technically have separate constituencies (but the parties typically submit the same candidates to all constituencies and the seats are apportioned at the national level).
That's incredibly rare as you mentioned, but it has happened before twice in Canada to the same Prime Minister though he remained Prime Minister.
Prime Minister William Lyon Mackenzie King lost his seat in York North in 1925 and his seat in Prince Albert in 1945 but went on to be Prime Minister on both occasions. However, his party lost their majority in Parliament on both occasions, though they won the by-election in 1925 and was the largest party in 1945.
Usually, leaders would only lose their seat if their party loses too, in which has occurred twice in Australia and once in the UK.
In the UK, Arthur Balfour lost his seat in Manchester East after the Conservative landslide defeat in 1906.
These examples are referenced from The Guardian.
Might be worth adding that, on both occasions, King returned to Parliament shortly thereafter by persuading a member of his party in a safe seat to resign so that King could stand there instead. (Ditto for @SleepingGod's answer).
In 2007 the Prime Minister of Australia John Howard lost his seat, but his party also lost the election. He is the second Australian Prime Minister to lose his sear in an election after Stanley Bruce in 1929.
The best example of a Prime Minister who lost his seat but remained prime minister is William Lyon Mackenzie King who lost his seat in in the 1925 Canadian general election and in the 1945 Canadian general election, but still kept the job as Prime Minister of Canada. He returned to parliament shortly after each of these elections by persuading a member of his own party to resign from a safe seat (which triggered a by-election) where he stood in turn and won.
Credit to Steve Melnikoff for point regarding how King returned to parliament in Canada
In the 2013 British Columbia provincial election, Christy Clark, the premier, lost her own seat to David Eby, even though the BC Liberal Party won a majority of 49 of the 85 seats in the legislature.
As a result, Ben Stewart resigned from his safe Liberal riding of Westside-Kelowna, effectively yielding his seat to her via a by-election. Clark resumed her role as premier, then appointed Stewart as a provincial representative to Beijing.
You could make the case that this "almost" happened to the Scottish National Party in the recent UK general election, and the situation would have been even closer to the OP's criterion if the SNP had become part of a coalition government.
The SNP remains the party with the largest number of Westminster MPs in Scotland (though reduced from 53 to 35 MPs in the 2017 election), but its former leader in Westminster, Angus Robertson, lost his seat to the Conservative candidate. The former party leader, Alex Salmond, also lost his Westminster seat.
Note, the current SNP party leader (Nicola Sturgeon) is an MSP in the Scottish Parliament, not at Westminster, and was therefore not a candidate in the Westminster election.
I’d like to point out the answer about Canada was wrong. Sitting Prime Ministers have lost their seats four times. The first time was in 1921 when Arthur Meighen lost his seat and the Conservatives, who had been in power since 1911, lost the election to William Lyon Mackenzie King. He had to run in another safe seat to sit in Parliament. Meighen then became the only sitting PM to lose his seat and the election a second time, in the 1926 election.
Meighen won the election of 1925, since he won the most seats, but could not form a government. King became PM when he formed a coalition with the Progressive party. Scandal forced him to resign, and a constitutional crisis was triggered when the Governor-General, Lord Byng, refused to allow a new election and invited Meighen to try to form a government. It lasted 88 days, and Meighen lost his seat in the next election and King and the Liberals formed the government again.
King lost his seat in the 1925 election, so he was the 2nd sitting PM to lose his seat, but still put together a coalition to form a government and was elected in a by-election in a safe seat after a resignation.
The 3rd time was Meighen’s loss in the 1926 election, and the fourth was King’s 1945 loss.
While not Parliamentary, this is close enough. Newt Gingrich, who was the US Speaker of the House, lost his position 1998 after his party lost only 5 seats. While that was not enough to cost them the majority (i.e. they still won overall), it was enough to spark a revolt within the party against a weak election showing they blamed him for. Gingrich, rather than lose an election for Speaker, resigned.
Also, Eric Cantor, House Majority Leader, neglected working hard in the primaries and wound up losing to a political newcomer, who then went on to win Cantor's seat in the 2014 Republican landslide.
Though the title isn't clear on this, the question is specifically about the leader of a party losing his seat in an election. Gingrich didn't lose his seat in the 1998 election.
@SteveMelnikoff Neither of these fit exactly, but are close enough. Gingrich won his seat, but he still resigned it after it became obvious he could not stay Speaker. I added Eric Cantor, which fits better (although still not Parliamentary)
In the US, Tom Foley was Speaker of the House and lost his race for reelection in 1994. However, his party also lost (so he would not have been Speaker if he had won).
More directly, Galusha A. Grow lost his bid for reelection in 1862. His party (Republicans) kept the House and he was replaced by another Republican, Schuyler Colfax.
Grow had replaced William Pennington as Speaker after Pennington lost his seat.
Something like nearly happened in North-Rhine-Westphalia in Germany recently, where the candidate for prime minister of the winning party, Armin Laschet, won his seat by only a slim margin (article in German).
If he had lost it, the party would have had to do some shenanigans to get him into parliament (e.g. some other winning candidate would have had to renounce his seat) since he must be a member of parliament to become prime minister.
While this is not a Westminster system (but it is mostly a parliamentary one), Romania has suffered a similar process just in the recent years:
in 2016 the Social Democrats won the Parliamentary elections and formed the Goverment. Their leader (Liviu Dragnea) wanted to be the PM, but this was prevented by having been convicted of election rigging. However, he remained head of the Chamber of Deputies (part of the Parliament) which virtually means the 3rd person of the state (after the President and the head of Senate). He was de facto running the Government
in May 2019, Dragnea was sentenced to jail and had to leave all positions (party leader, head of Chamber of Deputies).
as a bonus the subsequent PM (who also became the party leader) and her government has not managed to survive a motion of trust (no-confidence vote).