Business leaders say a Democratic sweep of the presidency and key Senate contests this fall could lead to major changes in U.S. labor law.

Business has viewed the Senate as a bulwark to bills backed by the AFL-CIO and other labor groups since Democrats took over Congress in 2006. Measures making it easier to form unions and strengthening the rights of workers to sue for discriminatory pay practices have passed the House. But they have not been able to win the votes necessary to move forward in the Senate.

Even if they had, a final bastion remained: President Bush's veto pen.

Next year, however, the dynamics could change dramatically if Sen. Barack Obama (D-Ill.) wins the presidency and Democrats edge closer to the 60 votes necessary to break a Senate filibuster.

"This is one of the most important elections the business community faces," said Bill Miller, a senior vice president at the U.S. Chamber of Commerce.

"If the Republicans lose four or five seats [in the Senate] some of the labor measures probably will succeed over the minority's wishes," said Jade West, senior vice president of government relations at the National Association of Wholesalers-Distributors...

But the issue business leaders most often mention in worried tones is the Employee Free Choice Act (EFCA), which would make it easier for workers to form unions by eliminating a requirement that unions be launched via a secret ballot vote.

A business coalition is already running ads in Maine and Minnesota, where it touts Sen. Norm Coleman's (R-Minn.) opposition to the bill. Coleman is in a tough contest with Democrat Al Franken, who, like most Democratic Senate candidates, is supporting EFCA.