I don't pretend to know the detailed mechanics of the procedure. But it was certainly my impression that had the (supposed) conservatives stuck together they could have thrown a big monkey wrench in Boner's selection as speaker
Which also brings up the question of why does the minority party (Dems) have any say so in picking the majority party's speaker?
Speaker is (theoretically) non-partisan. He represents the whole House.
Kevin McCarthy is the Republican leader, as Pelosi is the Democrats’.
The Speaker vote is a vote of the full house...and there is no rule that says you must vote for your party, and in fact, you can vote for people not even in the House.
The only way to beat Boehner with 16 votes was the Pelosi scenario I’ve described a couple times in this thread.