MIAMI — A federal judge said on Wednesday that he planned to block provisions of a Florida measure that made it harder for organizations to register voters in the state.

The measure, part of a broad and contentious 2011 election law in Florida, had a serious impact on third-party voter groups, like the League of Women Voters and Rock the Vote, which filed the suit along with the Florida Public Interest Research Group Education Fund. The groups asserted that the new requirements were onerous and made volunteers vulnerable to fines and even felony charges.

Voter registration, particularly among Democratic voters, declined significantly in the past year. The Florida Times-Union reported this week that the number of registered Democrats had increased by only 11,365 from July 1, 2011, to Aug. 1, 2012, a sharply lower figure than in the same periods during the past two presidential races. In 2004, nearly 159,000 new Democrats were registered in that period. In 2008, the number was nearly 260,000.