Updated

Union activists are rallying on Capitol Hill Wednesday in support of the Employee Free Choice Act that supporters say would make it easier for workers to unionize but opponents call a "card check" intended to intimidate.

The key provision stirring debate is a measure that eliminates the secret ballot that is now required in votes among employees deciding whether to organize.

Under current law if 50 percent of a company's workers sign union cards, the company may choose to recognize their workers as unionized. Otherwise, if 30 percent of the workers show interest in unionizing, the decision goes to a secret ballot, and if 50 percent vote for a union, then they can form one whether the company wants it or not.

Under the Employee Free Choice Act now up for debate, workers could still use the 30 percent mark to use a secret ballot route to unionize but if a majority signs union cards, then the workers would be unionized.  The company would have nothing to do with it.

Supporters and opponents say that is a much likelier scenario under the new law, and critics argue that it will result in workers being forced to sign cards even when they don't want to.

Among the supporters attending the rally were Sen. Tom Harkin, D-Iowa and Rep. George Miller, D-Calif. They say the bill protects employees from employer violations of labor laws.

Organizers said they brought a petition of more than 1 million signatures to urge Congress to pass the bill. Yet with about 16 million union members in the country, the petition represents only a fraction of organized workers supporting this effort.

The bill does have support of two powerful players: President Obama and his nominee for labor secretary, Rep. Hilda Solis, D-Calif. In fact, Solis co-sponsored the bill in the House last year and may run into opposition in her confirmation hearing because of her support for the measure.

The bill passed the House last year but didn't pass the Senate. With more Democrats in the Senate this go-round, it's possible the bill has enough support to get passed.

FOX News' Molly Henneberg contributed to this report.