Remember that a Speaker of the House is elected by the majority of house members present (not necessarily along party lines).

If Democrats have 216 seats in the House, and Republicans have 219 seats... then all Democrats would need is 3 Republicans to vote with them, and they can elect any Speaker of the House they want. That's the law.

Also, if 216 Democrats vote for one Speaker, 210 Republicans vote for McCarthy and 9 Republicans either don't vote or choose someone else... then Democrats win as the majority vote.

Theoretically, the House can have a Republican majority membership... and yet re-elect Nancy Pelosi as Speaker. It can happen.