I heard a man say mayor on the radio recently as though it were mayo (of the kind that one goes easy on) followed by ‘r’. I suspect that this weird pronunciation (which could only be adopted by someone who had never heard Larry the Lamb bleat at ‘Mr Mayor’) was influenced by mayoral.
Mayoral is almost always yoked with elections, especially with Boris Johnson around. Indeed mayoral and electoral are mispronounced on the same principle, with the stress on the or. That is no doubt an Americanism, but I think it is more often adopted by speakers who do not remember having heard the words pronounced at all. They see it in print often enough and then decide to make up a likely pronunciation.
Mayor has been a monosyllable since the 18th century, and Alexander Pope spelt it May’r lest there be any confusion.

Get Britain's best politics newsletters
Register to get The Spectator's insight and opinion straight to your inbox. You can then read two free articles each week.
Already a subscriber? Log in
Comments
Join the debate for just £1 a month
Be part of the conversation with other Spectator readers by getting your first three months for £3.
UNLOCK ACCESS Just £1 a monthAlready a subscriber? Log in