In the opening forum of the 2015 race for governor, three Republicans and a Democrat said state leaders have to restore voter confidence in how state road and bridge dollars are used before any major funding hike is feasible.

The key initial step, they said, is to end a wide range of diversions from the fund that is supposed to finance Louisiana’s transportation needs, including about $60 million per year that is sent to State Police.

The comments came during a two-hour forum sponsored by the American Council of Engineering Companies of Louisiana, Associated General Contractors of Louisiana and others.

The sole topic was state infrastructure needs, which meant that most of the focus was on Louisiana’s $12 billion backlog of road and bridge projects.

On hand were Republicans U.S. Sen. David Vitter, of Metairie; Lt. Gov. Jay Dardenne, of Baton Rouge; Public Service Commissioner Scott Angelle, of Breaux Bridge; and Democratic state Rep. John Bel Edwards, of Amite.

All four hope to succeed GOP Gov. Bobby Jindal, who cannot seek a third consecutive term.

The gathering was free of any sharp exchanges, which are likely to be common as the campaign unfolds.

However, Dardenne noted that Vitter’s proposal announced on Thursday to launch a “targeted highway building plan,” if he is elected governor, does not include a way to pay for it. “There is no accompanying dollars,” Dardenne after the forum.

“Obviously at some point, if you are going to propose a major initiative like that, you have to explain how you are going to pay for it,” he said.

Asked to respond, Vitter said in a brief interview, “I think this is years away, so I think it is sort of silly to suggest that I should have all the details and be dictating personally what we are going to do rather than building an idea and a proposal by reaching out to experts like in this room, citizens and legislators,” he said.

“I have been far more specific, far more concrete than anybody else on the stage, including Jay,” Vitter said.

The senator announced on Thursday that he would push “specific high-priority projects and specific revenue tied to completing them on an expedited basis.”

A special committee last week finished the brunt of its work on a monthslong study of possible fixes.

However, any proposals for the legislative session that begins on April 13 are expected to be modest, and all four contenders echoed similar views, at least in the short term.

Louisiana’s chief state source of transportation dollars is called the Transportation Trust Fund, or TTF.

But before it gets any injection of new dollars, candidates said, officials have to restore the trust of voters in how the money is spent.

Diverting those dollars to other state operations cripples any effort to generate new highway aid, Vitter said.

“It is completely destroying public trust in the TTF,” he said.

Dardenne said the $60 million per year in TTF dollars that go to State Police for traffic control far exceeds that need.

Angelle said that, when voters fill up their cars and trucks, they expect state gas tax dollars to finance road and bridge improvements.

Edwards said that, because of the State Police and other diversions, chances are “very, very remote” that voters would back additional transportation dollars.

Edwards also noted that about one penny of Louisiana’s 16-cents-per-gallon tax for rank-and-file projects is diverted to help pay off a 1989 highway and bridge bond issue called TIMED.

Others noted that state highway aid for parishes, which is supposed to be about $30 million per year, has crept up to about $46 million annually — another drain on state road and bridge revenue.

Angelle said the state should take another look at the “trigger” on a 2008 state law that would move about $400 million in car and truck sales tax revenue from the state general fund, where it is used for a wide range of services, to transportation only.

However, that only happens under certain state budget conditions.

Under current projections, that will be 2019 or later.

Edwards proposed boosting state aid for transportation from the capital improvements budget by $75 million per year for three years.

That aid and the $60 million from State Police would provide another $135 million per year for transportation and help ensure the $70 million or so needed for annual road and bridge preservation, he said.

Follow Will Sentell on Twitter, @WillSentell. For more coverage of Louisiana government and politics, follow our Politics blog at http://blogs.theadvocate.com/politicsblog.