WASHINGTON — A bipartisan Senate voted Friday to uphold a program that steers billions of dollars in transit construction projects to companies owned by minorities and women, striking a blow in favor of affirmative action programs under attack across the country.

In the first vote testing affirmative action sentiment in the 105th Congress, senators voted 58-37 to reject a conservative effort led by Sen. Mitch McConnell, R-Ky., to eliminate the Disadvantaged Business Enterprise program. That program, enacted under President Reagan in 1983, encourages the awarding of 10 percent of federal highway construction spending to women and minorities.

Maine Sens. Olympia Snowe and Susan Collins voted with the majority.

The vote reflected the complexities of casting an election-year vote on an often confusing issue that arouses strong feelings. Polls show that while most Americans favor giving minorities opportunities to compete, they oppose mandatory preferences such as quotas.

Voting to preserve the program were 43 Democrats and 15 Republicans; 36 Republicans and one Democrat voted “no.”

The lone Democrat voting for McConnell, Sen. Ernest Hollings of South Carolina, and six of the 15 Republican senators who voted against McConnell face re-election this fall. Another Republican who voted to preserve the program, Sen. Dirk Kempthorne, R-Idaho, is running for governor.

“The American people do feel strongly about it; they oppose quotas and set asides and timetables,” said Senate Majority Leader Trent Lott, R-Miss., who supported McConnell. Asked why most senators voted otherwise, he said, “Maybe it will take an election to get them in tune with America.”

“The people and the courts are ahead of Congress on race-based preferences,” said McConnell.

But President Clinton, who has launched a race initiative in recent months, detected a victory.

“Today’s vote reaffirms my administration’s `mend-it-don’t-end-it’ approach to affirmative action and promoting equal opportunity,” said Clinton.

Senate Minority Leader Tom Daschle, D-S.D., said the vote helps explain why Republicans have weaknesses among female and minority voters.

“A majority of Republicans said today that disadvantaged groups — women and minorities in particular — ought not be given the kinds of opportunities to participate fully in this economy,” he told reporters. “That’s what this debate was about.”

The outcome evoked outrage from some of McConnell’s conservative supporters.

“The Republican performance on this issue is pathetic,” said Clint Bolick, litigation director for the conservative Institute for Justice. He called Republicans who opposed the measure “unprincipled.”