Early Voting Map 2016

2016, 2016 Presidential Campaign, Colorado, Florida, Iowa, Nevada, North Carolina, Washington

35% of the votes cast for president in 2012 were cast before election day via early voting, absentee ballot voting and vote by mail elections. In 2016, 34 states and the District of Columbia offer no excuses early voting, either in person and/or by mail. Three states, Washington, Oregon, and Colorado, conduct their elections entirely by mail.

via Ballotpedia.com
The map below details early voting provisions in each of the states. The states displayed in dark red permit no-excuse early voting; the states shaded in yellow permit in-person absentee voting (an individual must provide a valid reason in order to qualify); the states shaded in dark gray permit neither no-excuse early voting nor in-person absentee voting; the states shaded in light gray conduct all voting by mail.

via NBC News
In terms of who wins, early voting makes a difference. In the past couple of presidential elections, the Democratic Party has benefited the most from early and absentee voting.

Below is the percentage of early/absentee voting in states in 2012 where it is available.
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via CBS News
A substantial portion of the vote will be cast before Election Day in some key battleground states. Colorado votes virtually all by mail – each registered voter is mailed a ballot. In 2012, 69 percent of the vote was cast early in Nevada, as were half of Florida’s votes.
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News stories about early voting, absentee voting and voting by mail

Reference and info on early voting, absentee voting and voting by mail