Republican-turned-Democratic Sen. Arlen Specter (Pa.) told a union rally Tuesday that a compromise union organizing bill will be sent to President Barack Obama’s desk by Jan. 1, according to the Associated Press.

“We have pounded out an employees’ choice bill which will meet labor’s objectives,— Specter said in a speech at Tuesday’s AFL-CIO convention in Pittsburgh, according to the AP.

The legislation, which would make it easier for workers to unionize, has encountered several false starts this year after Specter and other Senate moderates have vacillated on the contentious proposal.

Since switching parties earlier this year, Specter has backed away from his once-hard-line stance on the underlying bill, the Employee Free Choice Act, also known as “card check.— The measure would make it easier for employees to join unions and is viewed as a top labor industry priority this year.

During a highly publicized floor speech on March 24, Specter said he would not cast the deciding vote to cut off debate on the contentious legislation. “The problems of the recession would make this a particularly bad time to enact the Employee Free Choice Act. Employers understandably complain that adding such a burden would result in further job losses,— Specter said on the Senate floor earlier this year. “Knowing that I will not support cloture on this bill, Senators may choose to move on and amend the [National Labor Relations Act] as I have suggested or otherwise. This announcement should end the rumor mill that I have made some deal for my political advantage.—

Specter, up in 2010, bolted to the Democratic Party in April in the face of a difficult challenge from conservative former Rep. Pat Toomey (R-Pa.). Specter now faces a fierce Democratic primary challenge from Rep. Joe Sestak (D-Pa.), who is running to the ideological left of the five-term Senator and questioning his Democratic bona fides.

Despite his colleague’s prediction on Tuesday, Health, Education, Labor and Pensions Chairman Tom Harkin (D-Iowa) was less certain on the bill’s passage by the year’s end.

“You know, I’ve been working on it. That’s all I can say,— Harkin said.

Jessica Brady contributed to this report.