Early US Voting Begins in SeptemberElection Day in the United States is still two months away. But though U.S. political campaigns at times seem endless, voters in some states can begin casting votes this month — even before the first general-election debate. More than two-thirds of the country's 50 states allow a voter to cast a ballot in person before November 8, Election Day. All of them offer a way to vote by mail if the voter cannot make it to the polls that day. Most of the early voting states begin the process two or three weeks before the election, though voters in Minnesota and South Dakota can hand in their ballots as early as September 23.  A lot can happen in the final months of campaigning. Voters will be inundated with advertising and will have the opportunity to watch three debates between the presidential candidates and another featuring those running for vice president. A graph depicting the race between Democrat Hillary Clinton and Republican Donald Trump during the past year shows Clinton building a lead for four or six weeks at a time before a Trump rally that brings their poll numbers nearly together.  The most recent Trump surge is happening now after Clinton peaked in late August with a six-point lead. The latest polls put Clinton up by about four points nationally, even as she continues to narrowly lead in several key states that will likely determine who wins in November.  Those same polls continue to show that more than half of registered voters have an unfavorable view of both Clinton and Trump. Recent history as a gauge At this point in the 2012 presidential race, incumbent Barack Obama was about even with his Republican rival, Mitt Romney, in a range of national polls. But in the final two months, public opinion swung wildly.  Obama took a big lead for most of September; Romney briefly pulled ahead in early October before trailing the president by about one point on Election Day. Obama won the national popular vote by about four points. In 2004, President George W. Bush led then-senator John Kerry by six points in early September. But Kerry made a charge in October that year, trailing by only 1.5 points by the time November arrived. He lost to Bush by 2.5 points.