Washington ? Congress took a step Friday toward turning the nation’s capital city into the home of the first federally supported school voucher plan, an idea with implications across the country.

The House narrowly endorsed private-school vouchers for poor District of Columbia students Friday, a plan likely to win final approval when the city’s budget comes to a vote next week. The Senate, too, will soon consider a plan to let district students attend private school at public expense.

The last time proponents got this far, in 1997, the voucher proposal stalled in the Senate after a veto threat from then-President Clinton. This time, proponents say the idea may have enough support in the Senate, and the White House isn’t an obstacle: President Bush backs school choice.

If Congress adopts vouchers for one of the nation’s most troubled districts, it could influence the choices of state leaders and further energize those on both sides of the issue. Six states offer some form of vouchers, but voters in other states have soundly rejected them.

“Sometimes vouchers don’t get traction because they’re not in places anyone pays attention to. But for Washington, D.C., to house a program of choices, that could have tremendous traction,” said Jeanne Allen, president of the Center for Education Reform. “We’re closer than we’ve ever been.”

But to opponents, who say vouchers strip money from public schools, the fight isn’t close to over.

House Democrats say they believe the voucher vote could be overturned when the budget bill comes up for a vote next Tuesday. Democrats also say the close vote — 205 to 203 — signals the plan faces big trouble in the Senate.