BBCThe overnight results from Thursday's elections have confirmed the message of the polls that Reform are posing a major challenge to the traditional dominance of British politics enjoyed by the Conservatives and Labour.
The party won the Runcorn and Helsby by-election, just managing to overturn a 35-point Labour majority.
Meanwhile, Andrea Jenkyns, a former Tory minister, has convincingly won the new position of Mayor of Greater Lincolnshire. However, the party will be disappointed at narrowly losing out to Labour in the contests in Doncaster, North Tyneside, and the West of England.
Most of the local council elections are being counted later today. But early results also suggest Reform are heading for significant gains.
The party won 39% of the vote in the results declared so far, enough to put it well ahead of all if its rivals. And Reform also seems to have a good chance of winning overall control of both Lincolnshire and Staffordshire, both of which voted heavily for Brexit in 2016.
It is the first time an anti-EU party has won a by-election afresh. Until now the only by-elections won by an anti-EU party were two contests in 2014 when the local Tory MP stood down and fought the subsequent by-election under UKIP's colours.
Reform's seat gains have primarily been at the expense of the Conservatives. That was inevitable, given the party previously held nearly a thousand of the 1,641 seats up for grabs.
Nevertheless, the party will be deeply troubled at suffering a drubbing every bit as severe as the one it suffered in last year's general election.
On average its vote was down by 25 points since the last time these seats were fought in May 2021, falling most heavily where Reform did best. The party has so far lost more than half the seats it is trying to defend.
But if the results will likely intensify the debate about how the Conservatives should respond to the challenge from Reform, they also underline the message from the polls that support for Labour has fallen heavily since the general election.
Its three mayoral successes were all won on a significantly diminished share of the vote.
It is Labour's good fortune that it is defending fewer than 300 seats in the local council elections. Even so, and in contrast to the mayoral outcomes, the party has so far lost over half the seats it was trying to defend, mostly to Reform. Their vote is on average down on a poor performance in 2021 by as much as nine points.
Most of the hopes the Liberal Democrats and the Greens have for these elections are concentrated in the local council declarations later today. The overnight results suggest both parties are heading for a similar level of support as four years ago.
However, the Greens will be disappointed that their hopes of edging ahead of Labour in the race for West of England mayor were dashed, with the party finding itself instead trailing Reform in third place.
Indeed, narrow wins and losses were the order of the night. Nobody, it seems, dominates British politics any more.
John Curtice is Professor of Politics, University of Strathclyde, and Senior Fellow, National Centre for Social Research and 'The UK in a Changing Europe'.
Analysis by Patrick English, Steve Fisher, Robert Ford, and Lotte Hargrave.
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