US business leaders won’t be laughing if comedian Al Franken wins the legal wrangle keeping from taking his seat in the US Senate. He may be the deciding vote in over-riding Republican objections to the Employee Free Choice Act, a law that would make it far easier to unionise workplaces.

But controversial provisions that would discourage secret ballots and possibly allow unions to pressure undecided employees have business groups crying foul. They face an uphill fight. Unions are harnessing populist anger over the economy and Democratic control of both Congress and the White House to push aggressively for the passage. The 10 largest unions alone have given politicians about $280m since 1990, with about 95 per cent going to Democrats. Unions are also the largest supporters of so-called “527 groups” that skirt campaign contribution limits. A victory could usher in a union renaissance. Nationwide membership among workers has dropped to 12 per cent from more than 20 per cent a quarter century ago, with only the public sector ranks experiencing growth. Some 42 per cent of local government employees are unionised, against 8 per cent of private sector workers.