Some states have allowed primary votes to be cast as long as a month ago. In California, for example, up to half of all primary votes may be cast early.
Illinois's primary – along with those of 21 other states – is this Tuesday. But Lou Smith and Sam Sirko cast their votes for Sen. Barack Obama a week ago, during a three-week period in which Illinois offers early in-person voting.
While Mr. Sirko says his choice was made some time ago, Mr.. Smith only decided recently. "I was more teetering," says Smith, a physical therapist. The New Hampshire and South Carolina campaigns were what "really turned me off to Clinton."
In a primary season in which momentum and timing are coveted, it can be hard for candidates to know when to target certain voters. Thirty-four states now offer some form of no-excuse early or absentee voting, including about half of the Super Tuesday states. In delegate-rich California, half of all primary votes may be cast by mail the month before Feb. 5.