People lie on the sidewalk simulating a crime scene to symbolize the death of over 2,200 migrants in the desert over the last 20 years during a protest outside the office of Sen. John McCain, R-Ariz., in Tucson, Arizona, Wednesday, July 17, 2013. AP Photo/Valeria Fernandez WASHINGTON (AP) - Backers of comprehensive immigration legislation are gearing up for a campaign to push the House to act, even as some begin openly voicing fears they're already losing the fight. Congress' monthlong August recess could be crucial and supporters aim to exert influence in dozens of congressional districts home to Republican House members seen as open to reform. Business and religious groups and others with ties to the GOP majority are under pressure to win over lawmakers through tailor-made campaigns from within their districts, involving ministers, local executives and other contacts. Immigration activists, labor leaders and others on the left are making plans for large-scale mobilizations such as rallies and marches to exert pressure from without. "Here's the fact: We're not winning, so we've got to wage a campaign," said Sen. John McCain, R-Ariz., a lead author of the Senate-passed immigration bill. The scenario supporters hope to avoid is what happened to President Barack Obama's health care bill in the summer of 2009, when it was savaged by irate voters at unruly town hall meetings, taking a beating it never really recovered from. "August is a month in which either legislative proposals die, or they survive," said Sen. Robert Menendez, D-N.J. He said those who favor immigration legislation must be heard in August. Immigration legislation, a top priority for Obama, has been in limbo since the Senate last month passed a sweeping bill with provisions aimed at securing the border, requiring employers to verify their workers' legal status, allowing many more workers into the country legally, and offering eventual citizenship to the 11 million immigrants already in the country illegally. Instead, he's declared that the House will move in a piecemeal fashion, beginning with border security. When and how remained unclear, although Boehner said he hoped to see the House pass something before Congress next confronts raising the debt ceiling, which is expected sometime this fall. Authors of the Senate bill summoned dozens of business lobbyists, officials with religious groups and others to the Capitol earlier this week to tell them they needed to work harder and coordinate better to win over House Republicans. The senators distributed a list of 121 House Republicans seen as persuadable, and instructed those present to focus on tailoring individual campaigns for their congressional districts. "We are going to have numerous business contacts - whether it be a local restaurant that cares about immigration or a high-tech or manufacturing or financial business in their district - contacting them in terms of how important this is to the future of jobs in each district," said Sen. Chuck Schumer, D-N.Y. The coalition that supports immigration overhaul includes agriculture interests, businesses large and small, Catholics and evangelicals, high-profile Republicans, labor groups and others. By most measures, it dwarfs those opposed to reform, including tea party activists and lesser-known groups such as NumbersUSA, as well as some leading Republican voices. "We're up against a very shrill minority," said Charles Spies, a GOP fundraiser and co-founder of the group Republicans for Immigration Reform. Yet thus far, supporters have not translated their greater numbers and bigger budgets into a successful campaign to shift opinion among House Republicans. Some officials with outside groups say that until recently their attention was focused on the Senate, arguing that as they begin to make inroads in congressional districts their efforts will show. Joe Trauger, vice president of human resources policy at the National Association of Manufacturers, said his group is making plans for everything from plant tours for members of Congress to showing up at their town halls over August, all aimed at "making sure they understand there are folks out there that do support moving forward on immigration reform and want the House to proceed." That's not keeping some, on the right and left, from criticizing business in particular for failing to spend more money and push harder in the fight. "The business wing of the GOP has been outhustled by the anti-immigrant wing of the GOP for years," said Frank Sharry, executive director of America's Voice, which supports immigration reform. This is the moment, and they've really got to throw down. Yet some House Republicans say there's a limit to how much outside groups can influence their thinking anyway, saying they're more interested in what their constituents have to say.