8 Questions

Dan Balz on topics that will shape the 2012 campaign in the final 100 days

Question 5: Which groups of voters do the two campaigns care most about?

Mobilizing their bases will be the first priority for Obama and Romney. With so few truly undecided voters available this year, turning out committed supporters becomes as important as persuading those still wavering.

For Obama, that means making sure he gets huge turnout again among African Americans (his advisers are confident that he will), that he motivates Hispanics to come out in big numbers and wins at least 65 percent of their votes. His biggest challenge is likely to be among young voters, who were so enthusiastic four years ago and aren't so engaged this year.

Romney needs the conservative base of his party motivated. Though he sometimes struggled with some of these voters, particularly evangelical Christians, in the primaries, all signs suggest that their deep dislike of the president will be enough to get them to the polls. Romney also needs a big vote among white non-college voters, particularly men. They don't much like the president, but if the Obama campaign's attacks on Romney's business record stick, some of them might not vote for the challenger.

Many strategists outside the campaigns say women could hold the key to victory in November. In general, Obama will do better among unmarried women, while Romney will do better among married women. But there will be a real battle over independent women, particularly suburban mothers.

Of course, not all voters will be treated equally. Based on where advertising dollars are being spent, most of the attention will be focused on voters in fewer than 10 states.