Obama to supporters: Vote early, just like me Near the end of his two-day campaign blitz through six swing states, President Obama today will make a pit stop in Chicago to cast his ballot in the presidential race. Mr. Obama will be the first sitting president to vote early in person, and in doing so he is aiming to set an example for his supporters. Both the president and rival Mitt Romney are racing through battleground states in the final weeks of the election seeking not just to win over voters but -- in states with early voting -- to convince them to vote before November 6. Early voting has grown more popular in each recent election cycle, and this year should account for at least one third of the ballots cast, according to CBS News polling unit estimates. In 2008, when Mr. Obama decisively won a number of swing states, some polling experts said they knew he had won a week before the election because of early voting results. Polls suggest a closer race this year, and that bears out in the early voting results available so far. While more Democrats have voted in a few key states, Republicans have the edge in others. Obama campaign spokeswoman Jen Psaki told reporters Wednesday that Mr. Obama is "pounding the pavement" during his two-day trip "because he feels this is a pivotal time, and every single extra doorknob, every single extra phone call could make all the difference in what we think will be a razor-thin election." Early voting, she said, "is a big priority for us." The Romney campaign, meanwhile, argues that its "unprecedented" on-the-ground efforts are producing impressive early voting results. While it may be behind in a number of states now, the campaign says it will gain ground. "Past trends in Iowa, North Carolina, and Nevada show that Republicans turn out for early voting in greater numbers as we get closer to Election Day," Rick Wiley, political director for the Republican National Committee, said in a memo Wednesday. We've seen that already in Iowa and Ohio, and we are seeing the same trend develop again this year in North Carolina and Nevada, meaning the Republican advantage will grow in coming days. Moreover, our superior ground game and organization will continue to drive Republicans to vote early right up to Election Day.