Should public sector unions make campaign expenditures?

Diana Furchtgott-Roth has this:

With the close of the 2010 election campaign, the American Federation of State, County and Municipal Employees reached a new spending record, pouring $87 million into this congressional election.
AFSCME's $87 million is greater than the campaign spending by the U.S. Chamber of Commerce ($75 million) and American Crossroads ($65 million). Other public-sector unions, such as the Service Employees International Union ($44 million) and the National Education Association ($40 million) also ratcheted up their campaign spending.
AFSCME President Gerald McEntee is proud of his union's track record. Quoted in the Wall Street Journal, he declared, "We're spending big. And we're damn happy it's big. And our members are damn happy it's big -- it's their money." . . .