Loudoun County is about to make a historic choice about whether to join the Metro transit system, and it’s gratifying to report that the decision seems to be moving toward “yes.”

It’s not a done deal, but politicians appear to be listening to business leaders who stress that rail transit is needed to chart a more dynamic future for Loudoun beyond being merely a bedroom suburb for its neighbor and rival, Fairfax County.

Loudoun’s long-term identity has emerged as potentially the decisive factor as the Board of Supervisors plans to vote July 3 on whether to endorse extending the Silver Line beyond Dulles International Airport to two new stations in the county’s southeastern corner.

In particular, Loudoun’s young professionals have mobilized to push to bring Metro to the county because they want to rely on cars less than their parents did. Without transit access, they say, it won’t be possible to create robust commercial and night life districts close to home.

“This is a generational shift. I think our generation doesn’t want to live in these bedroom communities and then have to commute into work every day. We want to be able to work close to home and live close to entertainment,” said Victoria Rawlings, 29, vice chairman of the Young Professionals Committee of the Loudoun Chamber of Commerce.

Rawlings, an executive at an information technology consulting firm in Sterling, was one of several young business people who spoke strongly for the Silver Line at a lively, four-hour hearing in Leesburg last week.

Older representatives of the business establishment echoed their arguments. Without Metro, they said, Loudoun won’t be able to attract a top-quality workforce, and the jobs will go to Fairfax or elsewhere in the region.

“Our children prefer to live in walkable, multi-modal, mixed-use communities,” architect Alan L. Hansen told the June 4 session. “Many of our corporate and government clients will only consider sites served by Metro for relocation and expansion.”

Opponents continue to argue that the county can’t afford Metro, but they appear to be on the defensive. Metro proponents outnumbered critics by better than two to one at the hearing. A parade of business owners and professionals said the long-term benefit outweighed the price, and several volunteered to pay more in taxes to help cover the cost.

“I believe the board will make the right decision,” Board of Supervisors Chairman Scott K. York (R), who supports the plan, said in a telephone interview. “The hearing confirmed what I am seeing all around in the community, and that is there is just widespread support for rail coming into Loudoun County.”

The project got another boost last week on a controversial labor issue. The Metropolitan Washington Airports Authority, which is building the Silver Line, agreed to drop a pro-union construction provision that was anathema to Loudoun’s all-Republican board. (I urged the airports authority to make that change in a column in March.)

The wave of support for the Silver Line is highly welcome, not only for Loudoun’s future but also for the rest of the region. A “no” vote by the supervisors would at the least delay Phase 2 of the project, which is to extend the Silver Line from Reston to Dulles Airport and, preferably, beyond. Phase 1, which gets Metro to Reston, is scheduled to be finished in late 2013.

In addition, if Loudoun pulls out, it would mean that the rest of the Washington region would miss an opportunity to be linked by transit to one of our most economically vital jurisdictions. Keep in mind that fast-growing Loudoun has the highest median household income of any county in the nation.

One intriguing revelation at the hearing was the degree to which many in Loudoun see Metro as a critical tool to help them compete with Fairfax to attract business investment. Fairfax, whose population is more than triple that of Loudoun, already has eight Metro stations and is scheduled to get eight more when the Silver Line is completed.

Loudoun’s political and business communities have long resented paying for schools and other services for residents who then work in Fairfax. Getting a chunk of the Silver Line is a way to offset that.

“It gives us a chance to stick it to our neighbors to the east, instead of them arrogantly thanking us for educating their workers’ children,” Joe Paciulli, vice chairman of the Loudoun Economic Development Commission, said. “If we can live and work here, it’s a lot better than living here and working there.”

I’m taking a break. My column returns June 28. For previous columns, go to washingtonpost.com/mccartney.