RICHMOND, NOV. 2 -- Supporters of transportation pledge bonds began their final sprint today to win voters in Tuesday's balloting, their prospects darkened by late opposition from prominent state leaders and a new wariness among voters toward debt.

The three chairmen of the pledge-bond campaign -- Lt. Gov. Donald S. Beyer Jr., Attorney General Mary Sue Terry, both Democrats, and Republican state Sen. Robert E. Russell of Chesterfield -- canvassed the state by airplane, making stops in Tidewater, Roanoke and Alexandria.

Boosters hoped today's "fly-around," combined with a $110,000 television and radio campaign in the state's major markets, would be enough to lift the pledge-bond proposals, questions three and four on Tuesday's ballot, to victory.

But their cause may be in trouble, largely because of voter anxiety about the economy and anger at elected officials, activists on both sides of the issue believe. A recent poll conducted for pledge-bond supporters showed the referendums trailing badly, according to sources.

This week also brought the news that Virginia's two U.S. senators, Democrat Charles S. Robb and Republican John W. Warner, oppose pledge bonds. And a senior state legislator, Del. Alson C. Smith (D-Winchester), who had been listed in pro-pledge-bond literature as a supporter, said he planned to vote no.

Pledge bonds allow governments to borrow money to build roads, with the debt paid off by future collections from transportation taxes such as the gasoline tax or the sales tax on automobiles.

Ordinarily state and county governments must hold a referendum each time they wish to issue bonds, but Tuesday's twin ballot questions would allow the state legislature and county boards to incur debt without going to voters each time. Cities already have the right to incur debt under limited circumstances.

Gov. L. Douglas Wilder said he supports pledge bonds, but did not attend today's fly-around and has not campaigned heavily on their behalf.

"I think they're going down in a blaze," said John McGlennon, a Democratic activst and political scientist at the College of William and Mary. "I don't see any enthusiasm for the bonds among the people that would have to be excited."

Beyer acknowledged today that the pledge bonds aren't "the slam-dunk people thought last August" because of rising economic uncertainty.

But Beyer said he remains hopeful that supporters can convince a majority of voters -- particularly those in traffic-clogged Hampton Roads and Northern Virginia -- that "now is the time to be bold" because of the boost that better roads will have on the state economy.

Supporters liken the bonds to the money a family borrows to buy a house, but opponents say it is dangerous to give elected officials new power to incur debt.

News of Robb's opposition came as a surprise to many on both sides of the bond campaign, and some see it as a sign that buck-passing for a possible defeat already is underway. A letter from Dwight C. Holton, executive director of the pledge-bond campaign, to Robb was leaked anonymously to a Richmond newspaper last weekend, the first word many people got that Robb does not plan to vote for the measures.

Some supporters of Robb, an occasional Wilder foe who said he planned to stay quiet on the pledge-bond issue, believe that Wilder allies released word of his opposition so the senator could share some of the blame for their defeat.