State Del. Mary A. Marshall had her revenge in the great Northern. Virginia feud this morning, but two hors later Fairfax County legislators seemed to have won the last laugh -- with Marshall's unwitting help.

While Marshall believed she had held up Fairfax's top legislative priority, a seemingly unrelated bill sailed through the House of Delegates on a 100-to-0 vote. Only a few hours after voting for it did Marshall discover that the measure had been amended days before to accomplish the county's goal -- an end to a state-mandated limit on funds it may spend on the county roads.

"There's no cap at all," she murmured as she read the bill carefully this afternoon for the first time. "How clever."

The day's events were the latest in a rare General Assembly phenomenon, a bitter, regional feud that has spilled into public view. Fairfax legislators had accused Marshall, Arlington's senior Democratic delegate, of pressing a "vendetta" against them, while Marshall had called Fairfax's senators "idiots" for helping kill one of her bills in revenge.

This morning the House Roads Committee, on which Marshall sits, summarily postponed consideration of a bill specifically lifting Fairfax's spending limit. Marshall's threat to scuttle the measure had prompted Sen. Richard L. Saslaw (D-Fairfax) to help kill an unrelated Marshall bill Wednesday, but Marshall and her allies did not back down this morning.

"Young man," Roads Committee Chairman Donald A. McGlothlin Sr. (D-Grundy) told Saslaw as he shipped the Fairfax bill back to subcommittee, "we can play just as hardball as you can."

But early in the afternoon, the House gave final approval to the bill that, in its fine print, accomplished Fairfax's goal just as well as Saslaw's captive measure. Marshall said afterward that the bill, ostensibly concerning federal revenues sharing funds, was a "sleeper" -- that she had no idea what she was voting for when she joined in the vote.

"We didn't advertise the bill," Saslaw acknowledged later.

The issue behind the namecalling is the overloaded road system in fast-growing Fairfax County and the state's inability to fund all the needed street improvements. Two years ago the General Assembly gave Fairfax permission to spend as much as $10 million of its own money each year, with voter approval, to build, widen or repave its roads.

Fairfax voters since have approved spending $55 million for roads, and so this year the Board of Supervisors voted to ask the legislature to lift the $10 million cap. The state highway department supported the request but Marshall objected, saying Virginia would have to pick up the maintenance costs for any new roads the county builds.

Marshall's objections, vigorously attacked by Saslaw as an intrusion into Fairfax affairs, created the impasse that seemed to be building this morning. But Marshall did not realize that a bill by Sen. Frederick Gray (D-Chesterfield), intended to allow spending of revenue-sharing funds for local roads, had been amended at the request of a Fairfax lobbyist and Sen. Joseph V. Gartlan Jr. (D-Fairfax) to lift the $10 million cap as well.

While the Fairfax-Arlington fight was brewing, Gray's bill was slipping through the legislature with little notice and less discussion.

"The bill passed the House 100 to 0," Saslaw marveled this afternoon. "I didn't realize we had such broad-based support."