This, as we keep discovering, is an era of unexpected electoral results. Tuesday’s decision by Britain’s prime minister, Theresa May, to call a general election for June 8 was certainly unexpected. In an age in which few secrets remain secret, no journalist or politician seemed to have had an inkling about the announcement until it was made. But even in the era of the unexpected, it is difficult to see any result other than a solid Conservative Party victory, returning Mrs. May to Downing Street confirmed as prime minister.

The real question the June election will raise is not which party will form the next British government, but which party takes on the mantle of opposition?

There is certainly widespread disaffection with the Conservative government’s policies, from its cack-handed approach to Brexit negotiations to resentment over continuing cuts in public spending. Yet, disaffection with the opposition and, in particular, with the Labor Party, is far starker.

Labor is in disarray. It recently lost a parliamentary by-election in a traditionally rock-solid seat, has plummeted in opinion polls and is convulsed with infighting. A poll taken after Mrs. May’s election announcement showed a 21 percentage-point lead for the Conservatives over Labor. To put that in perspective, when Margaret Thatcher trounced Michael Foot in the 1983 election, seen as a nadir for Labor, she enjoyed a not quite 15-point lead.

Many see the Labor’s problems as deriving primarily from its leader, left-winger Jeremy Corbyn. Mr. Corbyn has been markedly ineffectual as leader, unable to enthuse even his core supporters. A recent poll suggested that fewer than 40 percent of Labor voters think he would make a better prime minister than Mrs. May.

One Labor member of Parliament, John Woodcock, told his constituents, “I will not countenance ever voting to make Jeremy Corbyn Britain’s prime minister.” When the party’s own lawmakers can’t face the idea of their leader as prime minister, it is difficult to know why anyone should vote Labor.

Labor’s crisis runs deeper, though, than its leader. It no longer knows what kind of party it is, or whom it seeks to represent. So it has been unable to take a stand on the big issues of the day, most notably Brexit. Fearful of losing its residual working-class base, the party shrank from full-hearted backing of the Remain campaign. Neither, though, can Labor — anxious not to alienate middle-class, urban voters — truly embrace Brexit.

The result has been an irresolution that has leached support from both constituencies. Labor’s vacillation over Brexit has led many middle-class liberals to switch to the Liberal Democrats, or simply drift away. Tony Blair has already called on voters to support anti-Brexit candidates, irrespective of party affiliation. There are reports that Labor’s former leader may campaign on this platform with the Liberal Democrat leader Tim Farron.

Decimated in the 2015 election, after its unhappy phase as the junior partner in a coalition government with David Cameron’s Conservatives, the Liberal Democrats have now repositioned themselves as the party of Europe. Making a play to win the support of the Remain voters who still feel resentful about the result of last year’s referendum on Britain’s membership in the European Union, it is calling for a second referendum at the end of the Brexit negotiations.

The Liberal Democrats may recoup some lost seats in Parliament, but its electoral appeal is too narrow for it to form a serious opposition. It would be triumph for the Liberal Democrats if they won back even 50 seats at the coming election.

As for the UK Independence Party, the Brexit vote has deprived it of a raison d’être. Since the referendum, the party has imploded in a vicious civil war. It currently has no representatives in Parliament, and is unlikely to have any after the June election either.

In Scotland, the governing party is the Scottish National Party. At the last general election, it won an extraordinary 56 out of 59 seats, leaving Labor, the Liberal Democrats and the Conservatives each with a single seat.

The party’s leader and Scotland’s first minister, Nicola Sturgeon, has tried to exploit the Brexit result to push for another referendum on Scottish independence, pointing out that a majority of Scots voted to remain in the European Union. Mrs. May has insisted that any referendum, if there is to be one, can only take place after Brexit negotiations are completed, and Britain has left the union. This conflict will cast a shadow over the coming election, but there is little evidence of much appetite among Scots either for a new referendum or for independence itself.

Given their extravagant success at the last election, it would not be surprising if the nationalists lost a few constituencies this time. As in England and Wales, though, the real battle will be not over who governs, but who, among a depleted opposition, can make the most of whatever political scraps remain.

Again, Labor is likely to fare worst. Twenty years ago, the party seemed unassailable in Scotland. Even as late as 2010, it held 41 out of Scotland’s 59 constituencies in the Westminster Parliament. After June 8, Labor may be left with not one.

This could, and should, have been a vital election, the focus for a great debate about the kind of post-Brexit Britain people want, a fierce contest over issues from austerity to immigration. But the void where an opposition should be means that little of substance will be debated.

To be sure, there will be shouting matches over Brexit, and many will try to use this election to rerun last year’s referendum. But after June 8, a Conservative government will enter into negotiations with the European Union with its policy and strategy barely tested in public.

Britain’s surprise general election comes amid a series of highly charged and unpredictable national votes — from the Brexit vote and American election last year, to the Dutch general election and the Turkish referendum this spring, and with the first round of the French presidential election, before the German federal elections in September.

All such democratic soundings should provide an important platform for public debate and a vital gauge of the popular will. A pity, then, if Britain’s election becomes the one that matters least.