This weekend will mark the end of Sir Keir Starmer’s first 100 days in Downing Street and the new Labour UK Government’s first 100 days in power. I suspect you will not need me to recount the Government’s issues in that period, from questionable donations and unpopular policymaking to the resignation of Sue Gray.

That rocky beginning may end with one silver lining, with Conservative MPs voting to put Kemi Badenoch and Richard Jenrick through to the vote of Conservative Party members. Badenoch is prone to starting monumentally stupid political fights, and Jenrick’s idea of sound strategy is to tack to the right of whatever position Nigel Farage holds. One Labour MP cheekily asked the Guardian’s Political Editor, Pippa Crerar, whether the result had to be declared as a gift.

But I suspect Downing Street is not celebrating yet. The days when a government could rely on an unelectable main Opposition party to keep it in power are potentially behind us, and the new government’s deepening unpopularity cannot be papered over as easily as it could have been in past election cycles.

Read more by Mark McGeoghegan

According to YouGov, net favourability towards Sir Keir stood at 0 in mid-July, following the election, but has since fallen to -36. The Government’s net approval rating has likewise declined from -2 in late July to -41 now, on par with the -40 YouGov recorded immediately before Boris Johnson’s resignation in June 2023, and favourability towards the Labour Party has fallen from +1 immediately after the election to -29 today. Around a third of those who voted Labour in July are now unfavourable towards Sir Keir and his party, and 39% disapprove of the government.

The overall picture in Scotland is similar. Sir Keir scores a -32, the Labour Party a -30, and net approval of the Government is -51. I wrote about the bet Sir Keir and his government are making last week: that delivery on the economy will, in turn, deliver the popular appeal it needs to hold on to power in 2029. Even delivery against relatively low expectations might be enough.

But Labour’s support at the most recent election was thin. Its vote share was the lowest to achieve an overall majority in the history of the House of Commons. As the pollster James Kanagasooriam has put it, Labour erected an electoral sandcastle - impressive, but prone to being washed out with the political tides. A similar bet on economic recovery made by the Biden administration did not pay off; despite objectively positive economic data, Americans feel worse off than they did under Trump. And in Europe, centrists who have bet on competent government to deliver popularity find themselves besieged by the far right.

And plenty of elections will come before Labour’s bet could pay off. Scotland and Wales go to the polls in 2026 for elections to the Scottish Parliament and Welsh Senedd. Both nations will hold local elections in 2027, and England will hold local elections of one kind or another every year of this Parliament.

All of this prompts the question: if Labour does not reverse its declining popularity, and a Badenoch or Jenrick-led Conservative Party cannot capitalise (on -40, the Conservative Party is even less popular than Labour), who might benefit?

We live in a time of historically low trust in politics and politicians, and these periods tend to produce plentiful opportunities for "outsider politics" and those who attack the establishment, advocating structural change or radical overhauls of policy. That does not necessarily mean populists, though populists often find it easiest to take advantage, as we have seen on the continent.

There is no single answer: different parties are better positioned to capitalise in different parts of the country. In Wales, support for Welsh Labour has fallen by around 11 points since the General Election, and  it now leads Plaid Cymru, the pro-independence Welsh nationalist party, by just a single point. The Conservatives have also fallen back since July, but both Plaid and Reform UK have made gains, and a Senedd election on the current polling would result in Labour and Plaid being nearly level on seats, with Reform third.

Keir Starmer's favourability rating has fallen to fallen to -36Keir Starmer's favourability rating has fallen to fallen to -36 (Image: PA)

In England, the beneficiaries of this scenario would likely be Reform and the Greens. Reform came second in 98 seats, 89 of which are currently held by Labour, meaning that in those parts of England, Reform can now position itself as the party to vote for in protest of the government. The Greens can do likewise in the 39 English seats where they came second, all to Labour. The Conservatives may try to out-Reform Reform, but historically, such strategies have further legitimised the populist right and facilitated their rise.

Scotland is somewhat different, as the most obvious beneficiary of an unpopular Labour government should be the SNP, but the SNP has its own problems and satisfaction with the Scottish Government is at an all-time low. The main question is, where do the right-leaning voters who switched from the Conservatives to Labour go now?

They are unlikely to return to the Conservatives without the constitutional issue at the top of the agenda. They have little reason to vote for a party with such a toxic brand. Yet, contrary to common assumptions about Scottish politics, there is roughly as great a demand for right-wing politics north of the Border as there is south of it. As the University of Edinburgh’s Dr Fraser McMillan has shown using British Election Study data, while Scots are slightly more likely to hold left-wing and socially liberal values than people in England, the gap is narrow.

It would be profoundly foolish to assume that, with unpopular governments at Holyrood and Westminster and a politically homeless Scottish right-wing, Reform wouldn’t benefit. Two post-election polls have had Reform level with the Conservatives at Holyrood, and one of those - by Opinium - would see Reform win roughly as many seats as the Conservatives in a Scottish Parliament election, potentially becoming Scotland’s third-largest party.

The British party system has not been shaken up in this way since the 1920s when the Liberals went into terminal decline and were supplanted by Labour. If Sir Keir’s bet does not pay off, we could be in for an even more significant shake-up, one that would benefit nationalists in Scotland and Wales, and the populist right everywhere.

Mark McGeoghegan is a Glasgow University researcher of nationalism and contentious politics and an Associate Member of the Centre on Constitutional Change. He can be found on BlueSky @markmcgeoghegan.bsky.social