On this Labor Day, unions are thinking about Election Day.

They’re looking for a candidate who will enforce their rights, expand their legal protections and not buckle under pressure.

They’re betting on Sen. Barack Obama. But even if he wins, their job will not be over.

Over the last few decades, companies have increasingly opposed unions, and many have gone to great — and illegal — lengths to block workers’ right to organize.

But the government has punished only a few companies — and then with just a slap on the wrist.

As a result, the percentage of the U.S. work force that’s unionized today is only 7.5 percent in the private sector, and 12 percent overall.

It’s not that workers don’t want to join unions. Some 60 million workers would join a union if they safely could, according to a December 2006 poll by Peter Hart.

So to make joining a union easier, labor is now calling for a different method of establishing new union bargaining units.

Legislation called the Employee Free Choice Act — which Sen. John McCain opposes and Obama supports — passed the House in 2007 but Republican senators blocked it from coming to a vote. It’s likely to come back up for a vote next year.

Under this bill, employers would be required to bargain with their employees as soon as a majority of them sign union authorization cards, eliminating the procedural delays and opportunities for interference that exist under the current law. Unions and employers unable to agree on a first contract would submit the dispute to binding arbitration.

The bill would also put some teeth into the law. Workers fired for union organizing would be eligible for “treble damages” — three times their lost pay — rather than just back pay. And other serious unfair labor practices would be punishable by $20,000 fines.

If Democrats gain additional Senate seats in November and Obama wins the White House, labor law reform will have its first real chance of passage in 30 years.

That’s why unions are pushing Democratic candidates at labor rallies all over the country this weekend.

But labor activists need to remember that elections aren’t a panacea.

In 1977-78, President Carter half-heartedly pushed for pro-worker amendments to the National Labor Relations Act, only to see them killed in a Senate filibuster.

Fourteen years later, President Clinton appointed a presidential commission to study labor law reform, thereby wasting the only two years during his presidency when Democrats controlled the House and Senate and could have introduced new legislation.

Will Obama be any different?

If he wins, he may try to avoid a knock-down, drag-out fight with corporate America during his first few months in office. Only grassroots pressure, now and then, can ensure that this bout occurs — and ends favorably for labor.

Then, next Labor Day, workers would have something to celebrate.

Steve Early is a Boston-based labor journalist and lawyer who worked for many years as a union organizer. He can be reached at pmproj@progressive.org.