Ohio has taken the lead in anticipation of the large turnout expected in this year's presidential election.
It's a one-page announcement from the Ohio Secretary of State, but here's the short version:
Those voting Republican will vote on Tuesday. Those voting Democratic will vote Wednesday. Independents and others will vote on Thursday.
Here's a link to the announcement: http://www.sos.state.oh.us/SOS/PressReleases/OhioVoting.pdf
Other battleground states are expected to follow Ohio's lead.