谢邀,大致上来说就是对于投票日时候有事(因为投票日就一天)不能到指定投票点投票的选民,可以选择提前去投票点投票。
http://www.ncsl.org/research/elections-and-campaigns/absentee-and-early-voting.aspx#early
More than two-thirds of the states--37, plus the District of Columbia--offer some sort of early voting. Early voting allows voters to visit an election official’s office or, in some states, other satellite voting locations, and cast a vote in person without offering an excuse for why the voter is unable to vote on Election Day. Some states also allow voters to receive, fill out and cast their absentee ballot in person at the elections office or at a satellite location rather than returning it through through the mail. This is often reffered to as in-person absentee voting. Satellite voting locations vary by state, and may include other county and state offices (besides the election official’s office), grocery stores, shopping malls, schools, libraries, and other locations. More detailed information can be found on NCSL'sState Laws Governing Early Voting page.
The time period for early voting varies from state to state:
The date on which early voting begins may be as early as 45 days before the election, or as late as the Friday before the election. The average starting time for early voting across all 34 states is 22 days before the election.Early voting typically ends just a few days before Election Day: seven days before the election in two states, on the Thursday before the election in one state, the Friday before in eight states, the Saturday before in seven states, and the Monday before Election Day in 13 states.Early voting periods range in length from four days to 45 days; the average across all 33 states is 19 days.
Of the states that allow early in-person voting, 22 and the District of Columbia allow some weekend early voting.