Most of the “new PM polling bounce” occurs before they take office

There has been a lot of discussion lately about Liz Truss’s expected ‘poll bounce’. Pundits argue that new Prime Ministers get a boost in support from voters as they introduce themselves to the country and announce policies setting the tone of their leadership. I have used polling data from PollBasePro and Politico to consider what this bounce might look like:

The plot above shows a surprisingly mixed picture. Only four Prime Ministers (Johnson, Brown, May and Douglas-Home) of the seven had higher support 30 days after taking office than on the day itself. Johnson is an outlier, with significant growth, probably due to abnormally low support for the Conservatives at the time of his election. May also had a substantial bounce, with her election coinciding with the aftermath of the EU Referendum and Labour’s coup.

Instead, most of the polling bounce seems to happen in the days before taking office. For John Major, for example, it was the removal of Margaret Thatcher that reversed Conservative fortunes, and by the time Major became PM the Conservatives had already reached the peak of their recovery.

Truss is an outlier in that support for the Conservatives fell during her long accession. With the Conservative leadership election being treated as a foregone conclusion by the end of July, any particular uptick in support should have begun to show up before September, when Truss became PM. Instead, the Conservatives have fallen a couple of points in polls.

If there is to be a Truss bounce, it is likely to come off the back of her freezing energy bills, or the death of Queen Elizabeth, rather than a strong endorsement of her personal leadership. It will be interesting to see how polls shift and I will continue to update the chart here.

This blog was cited in Ben Worthy’s Political Quarterly article on the fate of Liz Truss, here:

Worthy, B. (2022), Will Truss’s Time end in Failure? Assessing the Prospects of the latest ‘Takeover’ Prime Minister. The Political Quarterly. https://onlinelibrary.wiley.com/doi/full/10.1111/1467-923X.13199