Why did Turnout crater at the beginning of the 20th Century?

[jaichind]

I think it has to do with the introduction of Australian ballot which took place in 1892.  Local machine politics, before Australian ballot came into play, used all sort of incentives to get people to the polls and then give them a ballot where the person votes straight ticket for one party of another and then the person puts that ballot into the ballot box.  So all a political machine for party Y has to know is that person X is a for party Y, get him to the polls with promise of liquor, and give him their ticket and know that is a vote for the local politicans of party Y.  With Australian ballot, the person might very well vote for President for party Y but not vote for the local politicans of party Y that is paying for this.  Over time the local political machine lost the incentive of mass mobilization since they would not know it really represented a vote for themselves and instead focused on a narrow mobilization of known supportors of the said local political machine.