MILWAUKEE — Thousands of volunteers have raced to collect signatures near busy intersections and malls all over Wisconsin, at makeshift “drive-through” operations in parking lots, during Green Bay Packers viewing parties and New Year’s Eve pub crawls, and even at a fold-up table inside Milwaukee’s airport just off Concourse C.

By a state deadline on Tuesday, these volunteers, many of them Democrats and union supporters, say they will submit at least 720,000 names on petitions to recall Gov. Scott Walker, the Republican who curtailed collective bargaining rights for public workers, leading to a face-off in this state.

Only two governors in the nation’s history have lost their jobs in recalls, but Mr. Walker himself acknowledges that, presuming there are no major flaws in the petitions, a recall election appears likely. That puts his removal, which would have a vote in late spring or early summer, within the realm of possibility.

Politicians and political operatives far beyond Wisconsin will be watching closely, not just for what the recall effort may imply for other states’ leaders who are considering cuts to workers’ benefits and union powers as a way to solve budget problems, but also as a sign for the presidential race. Wisconsin was one of several pivotal Midwestern states that gave Barack Obama solid victories in 2008 but then elected Republicans, including Mr. Walker, in significant numbers in 2010. Money from outside the state is certain to pour in from both sides for the recall vote.