The lobbying frenzy is aimed at overcoming resistance among many Republicans in the House of Representatives to the biggest overhaul of U.S. immigration laws in nearly 30 years.
Immigration reform, President Barack Obama's top domestic priority, passed the Democratic-led Senate with bipartisan support but its prospects in the Republican-led House are bleak.
While House votes could still be a long way off, this week could prove critical, with House Republicans set to hold a closed-door meeting on immigration reform on Wednesday.
Many rank-and-file Republicans view a path to citizenship for 11 million undocumented immigrants - at the heart of the Senate bill - as "amnesty" for lawbreakers. But businesses, religious groups and other supporters say they are undaunted.
"I don't think they've seen our best effort yet," said Kevin Appleby, director of migration and refugee policy for the U.S. Conference of Catholic Bishops. Supporters of immigration reform say religious groups could prove influential with Republicans because of their close ties with lawmakers from the party.
Still, Appleby acknowledged that the signals out of the House were not positive. Because of that, he said, the Catholic bishops were prepared to "use every tool available" to persuade lawmakers to take up immigration reform.
That includes making sure that lawmakers hear from their bishops, either by letter or phone. The conference will also enlist the help of parishioners, Appleby said.
Technology groups have a goal of contacting the offices of each of the 435 House lawmakers, said Robert Hoffman, of the Information Technology Industry Council, a trade group.
But lobbyists and pro-immigration groups will spend most of their time trying to convince Republicans in areas with both conservative and moderate voters and those whose constituents rely on immigrant workers.
"Our strategy is to talk to those members of the House who we think can hear our message," said Ray Gilmer, a vice president with the United Fresh produce lobbying group, which represents companies like Sunkist.
The U.S. Chamber of Commerce has run ads in support of immigration reform and plans meetings on Capitol Hill. The National Association of Manufacturers will hold a session on Thursday to discuss immigration with congressional staff.
Labor and progressive groups are targeting seven House Republican leaders, including Speaker John Boehner and Illinois Representative Peter Roskam, as well as a handful of Republicans in states with larger populations of moderate and Democratic voters, such as Michael Grimm and Peter King of New York.