Meanwhile, a group of Republican senators is trying to have the 2010 census form include a question about citizenship. They are trying to set a precedent that congressional seats be reapportioned based on a count of citizens, rather than all residents.

The census issue is roiling Hispanic and immigrant rights groups. Major organizations and broadcasters are mounting a campaign for participation, but some activists argue that Democrats and Mr. Obama haven’t done enough to earn Hispanic support for the effort.

“The only thing left for the immigrant to bargain is something they want from the immigrant, and that is that the person be counted. If that person refuses to cooperate, refuses to participate, refuses to comply, now he has a modicum of leverage,” said Nativo Lopez, president of the Mexican American Political Association.

The Rev. Miguel Rivera, president of the National Coalition of Latino Clergy and Christian Leaders, is calling for a boycott specifically by illegal immigrants.