A truce of sorts has governed Washington’s eclectic transportation lobby for the past two decades.

Whenever Congress has considered rewriting the law that authorizes federal surface transportation programs, the roadbuilders, the transit operators, the state highway departments, the environmentalists, the bicyclists, the Chamber of Commerce, the trade unions, the preservationists and the truckers — as well as all the other groups with an interest in the highway bill, as it’s known colloquially — have for the most part joined hands rather than fought one another.

They could have battled among themselves for slices of the federal transportation budget. Instead, they have always pressed for a bigger pie — and bigger slices for everyone.

The big-tent approach has largely worked. The past three highway bills (1991, 1998 and 2005) were enacted with broad support from all corners of the transportation lobby, with overwhelming bipartisan backing and with more money for everyone.

But as work on the next highway bill gears up this summer, Congress is staring at trillion-dollar-plus annual deficits — budget gaps that have never been seen since Dwight D. Eisenhower signed the 1956 law that created the Interstate Highway System. For the transportation lobby, the “Kumbaya” days may be drawing to a close. And this time, the circle will not be getting bigger. The key committee in the Democratic Senate is suggesting flat funding, at best, while the transportation panel in the Republican House is drafting the latest highway bill with reduced spending.

Facing a smaller pie for the first time in the history of the highway program, the past beneficiaries of so much federal largess are likelier than ever before to focus on minimizing shrinkage of their own slices, even if it means advocating cuts for the other guys. An earmark ban that all sides accepted will further complicate lobbying efforts and make it harder for lawmakers to grease the legislative wheels.

“You can buy everybody off if you can afford to buy everyone off,” said Ronald Utt, a transportation expert at the conservative think tank the Heritage Foundation. “The question is, have we reached the point that you can’t afford to buy everyone off? I don’t know if we’re there yet, but we’re getting close.”

All Together Now

Once the province solely of roadbuilders, the highway bill began shifting to a broader portfolio of transportation programs in 1982, when President Ronald Reagan’s intrepid Transportation secretary, Drew Lewis, sought to widen the political support for a 5-cent increase in the federal gasoline excise tax by promising 20 percent of the new revenues to transit systems. The move brought big-city mayors as well as urban Democratic representatives into the coalition. Transit operators over the next few years successfully carved out 20 percent of all federal gas tax revenues for their systems.

In 1991, the Democratic chairmen of the two committees that were writing the transportation bill — New York’s Daniel Patrick Moynihan in the Senate and New Jersey’s Robert Roe in the House — further expanded the highway bill coalition by writing in funding carve-outs for a variety of groups, including historic preservationists, cycling enthusiasts and environmentalists. As money flowed into the federal highway accounts, lawmakers used the extra dollars to buy off states that felt shortchanged by the federal formula for distributing transportation funds. They also set aside billions of dollars for thousands of local projects through earmarks. Roadbuilders and state highway departments grumbled about all the hands in the honey jar, but they went along because they kept getting more and more money.

The 1998 and 2005 bills followed the Moynihan-Roe model, ­funneling more money to roadbuilders while also setting aside more dollars for various other groups. To get the most it could in the 2005 negotiations, the highway bill coalition initially rallied behind a $375 billion measure funded by a gas tax increase — a 72 percent hike from the $218 billion 1998 bill. That astronomical starting point served the coalition well. It ultimately settled for a $287 billion bill, still a 31 percent increase.

Such funding hikes allowed the 2005 bill to support thousands of earmarked projects requested by lawmakers and dozens of targeted programs for roads, transit systems, bike paths, sidewalks and other infrastructure projects. Robert Poole, a transportation analyst with the libertarian Reason Foundation, estimates that roughly a third of federal highway dollars are now spent on projects other than road construction and maintenance.

“I see this as part of the overall fiscal mess the federal government has evolved into over the past several decades,” Poole said. “It’s not only that entitlements are beyond the government’s means to afford, but other programs like the transportation program have tried to be all things to all people, especially since 1991. We can’t afford that anymore.”

End of the Easy Road

The federal fiscal crisis started to affect transportation programs three years ago, when the economy tanked and dedicated gas and vehicle tax revenue fell off. In 2008, Congress began infusing the Highway Trust Fund with general funds from the Treasury. Lawmakers have propped up the transportation programs with $35 billion in such infusions since then and will have to do so again this fall — or agree to begin making cuts.

Deron Lovaas, federal transportation policy director for the environmentalist Natural Resources Defense Council, sees just two options for the transportation lobby and for Congress if cuts are unavoidable. One is for an equal, across-the-board trim to all the programs funded by the Highway Trust Fund. Under that scenario, environmentalists would join hands with the roadbuilders, the transit operators and other stakeholders and agree to stick together on the way down, just as they did on the way up. The other option is for targeted cuts or the elimination of particular programs. Under that scenario, it would be every lobbyist for himself.

With the Transportation and Infrastructure Committee in the House and the Environment and Public Works Committee in the Senate drafting legislation this summer, those two options are about to be tested.

“The problem with the circular firing squad with this bill, if past is prologue, is that you need a big-tent coalition to get these bills passed,” Lovaas said. “You really need as much support as possible for this to get through Congress and for the president to sign it, which means that this is may be, counterintuitively, when the bill can least afford a circular firing squad. This is when you need everyone to circle the wagons against a hostile outside context.”

Based on conversations with other groups, Lovaas is optimistic that the traditional highway bill coalition will hold together. “There’s not a real sign, at least among the interest groups, of an interest in divisive food fights,” Lovaas said.

But others see signs that the groups may turn against one another. Poole, who argues that the trust fund should be used more exclusively for Interstate construction and maintenance and that other programs should fight for general funds from the Treasury, said the downward pressure on transportation accounts will force state highway departments, roadbuilders and highway users to rethink their willingness to support transit and other programs.

“They’ve gone along with it because there was always a net increase in highway funding,” Poole said. “Now they’re looking much more skeptically at these things.”

For their part, transit operators can remind roadbuilders of an episode in 1999, when the Clinton administration proposed diverting more funds from highways to transit. William Millar, the president of the American Public Transportation Association, opposed the administration, arguing that the roughly 80-20 split should still hold even though his members could have benefited from the increase. Millar is still the head of the transit group.

But even if the lobbyists try to stay united, lawmakers in Congress may not. The House’s 87 Republican freshmen, so many of whom found their voice or at last their crucial backing in the tea party movement, may be more receptive than their veteran colleagues to arguments that some programs are ripe for reduction or elimination. “Everybody who has some claim on the transportation budget, whether for covered bridge repairs or for regular bridge repairs or for metropolitan planning organizations, is going to be actively out there pushing for the preservation of their program at current levels or higher levels,” Utt said. “My gut feeling is that for the first time in probably two or three reauthorizations you may see some programs judged to be more important than others and some either consolidated out of existence or facing fairly significant cuts relative to what they are now.”

The congressional committee leaders’ pledge to swear off earmarks also could weaken their ability to put together overwhelming support for the legislation. Rank-and-file members will no longer rally behind the bill to protect pet projects included for their home districts and favorite causes. “Elimination of earmarks is on balance good policy and good politics,” Lovaas said. “And it also makes passage more difficult.”

At House Transportation hearings earlier this year, each group in the highway bill coalition was given the opportunity to make a pitch for its own wish list. Despite clear instructions of the chairman, Florida Republican John Mica, to prepare to make do with less, many lobbyists still argued that they needed dramatic increases in funding to maintain infrastructure built across the country under previous highway bills. Some noted that the federal gas tax hasn’t increased since 1993, and others pushed for a variety of additional financing mechanisms, from tolls to infrastructure banks to public-private ventures.

In the past, shooting for the moon worked for the transportation lobby. More money always came. But now, with deficit reduction the only talk in town, with drivers paying $4 for a gallon of gas, with voters unwilling to stomach higher taxes or deeper federal debt, the reality of budget cuts is looming over the highway bill’s many beneficiaries for the first time.

“We’re at a watershed moment looking at the next reauthorization,” Poole said. “This will be one of the classic battles of the past several decades.”