The elections are seen as a test of support for Johnson, who became the first British leader in living memory to have broken the law while in office when he was fined last month for attending a birthday gathering in his office in 2020.
But some lawmakers among Johnson's governing Conservatives say that while the party may perform badly in some of its traditional supportive regions in south-east England, critics may not have the numbers to trigger a coup against the prime minister. But with the main opposition Labour Party trying to press its criticism of the government's response to the cost-of-living crisis, a poor performance could embolden critics in his party who wonder if he is still an electoral asset ahead of the next general election that must be held before the end of 2024.