As congressional campaigns roll into their final weeks, construction-industry officials are watching to see whether Republicans will take control of the Senate or Democrats will hang on to their majority. A GOP Senate win would put the party in charge of both houses of Congress.

But if Republicans do take the Senate, they won't have a clear field. Analysts don't think the GOP will gain enough Senate seats to get a filibuster-proof 60 votes. Nor are Republicans expected to score the two-thirds majorities needed in both chambers to override presidential vetoes. The result probably would be continued staandoffs on many issues. But industry officials say infrastructure bills will be an exception, commanding enough bipartisan support to break through gridlock.

Republicans need a net gain of at least six seats for a Senate majority. Forecasters say the GOP will pick up four to eight seats. But the battle for Senate control may not be resolved at the end of Nov. 4. Larry Sabato of the University of Virginia's Center for Politics says tight races in Georgia and Louisiana may result in runoff elections.

A Republican-controlled Congress could pass bills to curb or undo environmental and labor policies that businesses oppose. Marco Giamberardino, National Electrical Contractors Association executive director for government affairs, says, "I think what you'll see are some 'messaging' bills that Congress will pass." But President Obama probably will object to some of them. Giamberardino says, "You will see the veto pen come out more than you have in the past six years." The GOP probably won't be able to override vetoes.

Steve Hall, American Council of Engineering Companies vice president of government affairs, says narrow congressional majorities also could mean more partisan stalemates in areas such as tax reform, the budget or health care.

Still, Hall and other veteran industry lobbyists say infrastructure bills, particularly in transportation, have a good chance of congressional passage. The White House's strong pro-infrastructure rhetoric could give such measures a smooth path to enactment.

David Bauer, American Road & Transportation Builders Association senior vice president for government relations, says, "Regardless of the outcome of the election, this still remains one of the few areas [that show] a demonstrable history of both sides coming together." For example, says Pam Whitted, National Stone, Sand & Gravel Association senior vice president for government and regulatory affairs, "Look at the bipartisan vote on that Water Resources Reform and Development Act—it was overwhelming." That $12-billion authorization for Corps of Engineers water projects cleared the Senate 91-7 and the House 412-4.

Whatever the makeup of the new 114th Congress, its top infrastructure task, by far, will be reauthorizing federal highway and transit programs. The current surface-transportation extension lapses on May 31. Construction officials are pushing for a long-term bill with enough new revenue, from some source, to solidify the fragile Highway Trust Fund for several years. Many in the industry hope lawmakers will deal with the issue in the lame-duck session, set to begin on Nov. 12. But solving the revenue problem isn't likely by December's end.

Another big infrastructure measure on the 2015 agenda is a bill to renew Federal Aviation Administration programs, including airport construction grants. The current FAA law expires on Sept. 30. Airport groups already are campaigning to boost the passenger facility charge, which funds infrastructure.

Must-pass legislation next year also includes appropriations for all federal programs, including construction accounts, for fiscal 2016. First, in the lame duck, Congress will have to address appropriations for the rest of fiscal 2015. The current stopgap runs out on Dec. 11.

Some officials foresee bipartisan collaboration. "There is pressure on both sides of the aisle to start doing something," Whitted says. "So, no matter what party's in, they're going to have to be more open to working with the other side because, I think, their constituents are demanding it."

Jay Farrar, director of Bechtel's Washington, D.C., office, recalls the Clinton administration years, when Republicans controlled both chambers and a Democrat held the White House. "Clinton had to come Congress's way, and they basically made deals," Farrar says. "He got some things, and the Republican Congress got some things."

But Tom Flynn, United Brotherhood of Carpenters political director, is skeptical. He says a thin Republican Senate majority will make the political environment only "more toxic."