There are few surprises here. Barack Obama broadly supports expanding labor's right to organize, including the Employee Free Choice Act, which would allow workers to form unions by simply collecting signatures from a majority of the workforce. He also supports raising the minimum wage and indexing it to inflation.
Republican rival John McCain seldom mentions these sorts of workplace issues in the presidential campaign (they're not discussed on his website, suggesting his labor agenda is more likely reactive than proactive. However, on labor and workplace legislation, his sympathies lie mostly with business interests. He opposes the Employee Free Choice Act.
THE OBAMA AGENDA, IN DETAIL
Barack Obama supports labor's right to organize on several fronts. He co-sponsored (along with nearly every other Senate Democrat) the Employee Free Choice Act, which would allow a card check (the signatures of a majority of the workforce) to determine whether a union is formed, replacing the secret ballot. He would "fight attacks on workers' rights to organize," especially at the National Labor Relations Board. He also supports a ban on permanently replacing striking workers.
Additionally, Obama would raise (pdf file, right-click to save) the minimum wage to $9.50 by 2011, and index it to inflation. He backs expanding the Family and Medical Leave Act. Obama would require companies that wrongly classify employees as independent contractors to pay back taxes. He would beef up the Occupational Safety and Health Administration and Equal Employment Opportunity Commission, and improve whistleblower protection. He supports legislation to ensure that women receive equal pay for equal work and to prohibit discrimination based on sexual orientation or gender identity.
The Obama Record: Obama is endorsed by every major union, and rates highly on labor's legislative scorecards. Conversely, the Alliance For Worker Freedom, an organization dedicated to the "promotion of free and open labor markets," has rated Obama at the bottom of the Senate in each of the three years he's served there.
Though McCain hasn't had much to say on workplace issues, he does support flexible work arrangements, and would establish a "National Commission on Workplace Flexibility and Choice." Among other things, the commission would lay out a blueprint for "modernizing the nation's labor laws so that they allow for more flexible scheduling arrangements" and ensuring they don't limit working at home.
McCain opposes the Employee Free Choice Act; he called it an "assault on democracy" as he moved to block a vote on it in 2007. (He called on the Senate to pass instead the "Secret Ballot Protection Act of 2007," which he co-sponsored.) Moreover, in his Congressional career, McCain has largely supported business interests on labor legislation -- he supported the Alliance For Worker Freedom on key votes at least 80 percent of the time in each of the last three years. (One exception: he ultimately voted in favor of the Family and Medical Leave Act in 1993 -- although, according to the AFL-CIO, not before supporting an unsuccessful amendment to weaken it first. He now opposes its expansion.)
DOES IT MATTER?
Probably not. Though proponents of the Employee Free Choice Act call their bill "bipartisan," the Republican caucus was nearly united in its effort to filibuster the bill in the Senate. (Only Arlen Specter of Pennsylvania voted in favor of ending debate.) Even if Democrats pick up five seats in the November election, they're still not likely to succeed in bringing the bill up for a vote.
The National Federation of Independent Business has several other legislative priorities that reflect a general wariness toward government mandates on employers. With the exceptions described above, neither candidate has had much to say about these, which would suggest that despite the efforts of the labor movement, there will be little movement on these issues on Capitol Hill.
In the face of Congressional inaction, however, there are a couple places where the candidates' positions do matter: the Department of Labor and the National Labor Relations Board. McCain hasn't brought it up, but Obama promises to "ensure that his labor appointees support workers' rights."