While the majority party has elected their nominee on the first ballot over the past century, this year could be different.
Members vote "viva voice," meaning they stand when their names are called by a reading clerk and verbally announce who they are voting for.
Members can vote for anyone (even people who are not members of the House), vote present, or not vote at all.
If every member doesn't show up, or if some vote present instead of supporting a candidate, that decreases what the majority vote needs to be.
Political parties are much stronger now than they were then, when House members were often more loyal to their region.