Three weeks ago, it was a light-rail line, or perhaps a busway.

Now, it might simply be buses running down existing streets.

Transportation Secretary Robert L. Flanagan's March 13 announcement that the project had been selected to compete for federal transit aid was a big victory for Purple Line supporters.

But then he added that the state would spend another year studying whether the initial segment should run along existing streets instead of along a former freight railway turned bike trail that cuts across a leafy section of Chevy Chase.

In a last-minute twist that unfolded as Gov. Robert L. Ehrlich Jr.'s aides put the final touches on the state's transportation priority list, Flanagan found a way to mollify a well-connected Republican county councilman, shield Ehrlich (R) from charges he had abandoned a campaign promise to protect the bike trail and still leave open the option to proceed with the original route.

Here is what happened:

Two weeks ago, supporters of the project were hopeful that Flanagan had found a compromise that would allow the transit line to be built along the bike trail route while addressing the concerns of neighbors.

The Ehrlich administration floated a proposal to spend an extra $50 million for "cut-and-cover" construction that would bury the line where it bisected a country club and crossed back yards in neighborhoods. The added cost would be more than offset if light-rail trains were replaced with less costly, environmentally friendly buses.

The compromise seemed workable. After all, Dels. John Adams Hurson (D-Dist. 18) of Chevy Chase and Richard S. Madaleno Jr. (D-Dist. 18) of Kensington were rounding up support in the House for a bill to require cut-and-cover construction if the transit line ran along the trail.

But opponents, including Montgomery County Councilman Howard A. Denis (R-Dist. 1) of Chevy Chase, told Flanagan in a March 10 meeting that his compromise was not acceptable.

Meanwhile, Flanagan called Hurson and asked to meet with him. He asked Hurson to lay out his long-held proposal to run the transit line north from downtown Bethesda to the National Naval Medical Center, then east along Jones Bridge Road, rejoining the trail just before it crossed Rock Creek Park -- completely avoiding the country club.

Hurson had pushed the Jones Bridge route as an alternative light-rail line in 2000, but state transportation officials rejected it. Now that Flanagan was considering replacing light rail with buses, the route should be re-examined, Hurson said.

Transportation Department officials said the new route would add only a half-mile to the trip between Bethesda and Silver Spring and could include the construction of underpasses to bypass congested intersections.

So Flanagan crafted a two-pronged solution: Study the alternative route, but leave open the option of using the trail as a busway or light-rail line.

The strategy bought the Ehrlich administration another year to sidestep the controversy and avoid angering potential supporters in an affluent part of the county where the Republican Party hopes to make inroads.

Hurson said the extra year also provides time to study options for building the second leg of the Purple Line, which would extend to New Carrollton in Prince George's County, and how it would be integrated with the initial line from Bethesda to Silver Spring.

Hurson denied he gave up anything to win Flanagan's support, though he conceded that Ehrlich's chief of staff asked him -- unsuccessfully -- to throw his support behind the governor's controversial proposal to legalize slot machines.

"There's no quid pro quo," said Hurson, who is generally opposed to slots.

Ehrlich spokesman Paul E. Schurick called Hurson "a very good guy who is in great standing with this administration."

Flanagan spent several hours on March 17 walking the trail with Hurson and taking a tour of Jones Bridge Road. He clearly did not know the details of Hurson's route but appeared enthusiastic about the idea. He also expressed concerns several times about harming the trail.

"This area is pretty built-up," he said, "and this trail is a treasure.