Its flashing message was “Praying for immigrants. Praying for Congress.” Groups of evangelical Christians prayed on the Capitol lawn for the Senate to pass its bill. Mr. Noorani’s group, the National Immigration Forum, has worked with Southern Baptists and other large evangelical denominations to coordinate prayer campaigns and run pro-overhaul spots on Christian radio stations in states where lawmakers might be persuaded to change their views.

“In 2007, we weren’t even on the radar,” said the Rev. Samuel Rodríguez, the president of the National Hispanic Christian Leadership Conference, an evangelical group. Mr. Rodríguez said he had been on the road continuously, addressing primarily non-Hispanic Christian conferences to spread the message on the overhaul.

Business groups are also pledging to stay in the fray.

“What will shock a lot of people in the House is the level of interest and intensity of the business community compared to 2007,” said Scott Corley, the executive director of Compete America, which represents tech companies that are pressing for an increase in visas for skilled immigrants.