Majority of votes not mandatory for Speaker
>In two instances the House agreed to choose and subsequently did choose a Speaker by a plurality
>In 1849 the House had been in session 19 days without being able to elect a Speaker, no candidate having received a majority of the votes cast
>Finally, after the fifty-ninth ballot, the House adopted a resolution declaring that a Speaker could be elected by a plurality
In 1856 the House again struggled over the election of a Speaker. Ballots numbering 129 had been taken without any candidate receiving a majority of the votes cast. The House then adopted a resolution permitting the election to be decided by a plurality
https://www.govinfo.gov/content/pkg/GPO-HPRACTICE-108/html/GPO-HPRACTICE-108-35.htm