It took more than a decade of painstaking, bipartisan efforts led by a Northern Virginia Republican to win vital federal funding for the Metro transit system. Now, the money might dry up after flowing for only a year.

The $150 million annual payment has become one of the many hostages of a struggle within the Republican Party, between those willing to invest in worthy projects for the future and those who would sacrifice even sensible ones in their drive to shrink government.

Congressional Democrats want to continue providing the Metro money. Its fate will depend on whether enough Republicans in the House ultimately go along in a legislative struggle likely to stretch into spring.

The internal GOP differences are evident in the positions that Virginia Republicans are taking. Gov. Bob McDonnell and Rep. Frank Wolf, whose district includes parts of Fairfax and Loudoun counties, would protect the Metro funding but slash spending elsewhere. Rep. Eric Cantor, the House majority leader, most of whose constituents live near Richmond, says that, for now, the Metro cuts can't be helped given the need to reduce the federal deficit.

Our region should pay close attention to who comes out on top. That's partly because the result will cast light on whether the Republicans represent our region's interests well - a case they're eager to make in hopes of carrying Virginia in the 2012 presidential election.

It would be a huge step backward for our area to lose the federal money for Metro. It would mean giving up on buying needed new buses and rail cars and renovating outdated facilities, including a bus garage on 14th Street NW that's 103 years old. Richard Sarles, Metro's chief executive, says that he wouldn't sacrifice safety if the money disappeared but that service and reliability would suffer for sure.

Actually, it's already a significant setback that we have to reopen this debate at all. Congress authorized this chunk of financing - which is necessary but insufficient for Metro's long-term needs - through 2019. As part of the deal, the three jurisdictions served by Metro (the District, Maryland and Virginia) agreed to match the money by kicking in an additional $50 million apiece annually. With that supposedly settled, Metro was free to move on to other pressing issues.

The catch was that the money has to be appropriated every year. The new Republican majority in the House has proposed, and is expected to pass, a bill stripping out the federal money for Metro for the rest of the fiscal year ending Sept. 30.

The Democrat-controlled Senate is likely to try to restore the money, and Metro supporters are hoping that the House will ultimately leave it there when the competing spending proposals are sorted out in conference.

In a major push to save the funds, Metro is tapping the local business community and Metro's corporate suppliers. Sarles got a favorable reception when he made his case last week to directors of the Greater Washington Board of Trade. Metro is also hoping that Kawasaki, which supplies rail cars to Metro, will lobby congressional representatives from districts where it has facilities in Nebraska and New York. It's also asked New Flyer, a bus supplier, to do the same in Minnesota.

Republican Tom Davis, the former Fairfax congressman who sponsored the Metro funding bill that finally passed in 2008, said he thinks many in his party will eventually come around and support the program.

"This is just the first volley. This is not the endgame. You've got a lot of members for whom these budgets cuts now are just lines on a piece of paper," Davis said.

McDonnell also predicted that Senate action would mean the money would be restored in the end, and he said he'd favor doing so. The Metro funds are part of a set of "prudent investments in infrastructure" that "would be good to preserve," McDonnell told Washington Post editors and reporters Tuesday in Richmond. He'd prefer to see Congress attack the deficit through the "heavy lifting" needed to cut entitlement spending - such as for Social Security, Medicare and Medicaid.

I wish I could be so confident that the Metro money will be safe. I'm skeptical partly because Cantor had a very different response when I sent his office a list of questions about the Metro funds.

I asked why the GOP was stripping out the money when the original law had bipartisan support. I suggested that the federal government had an obligation to support Metro, given that about 40 percent of the system's riders are federal workers.

In return, I received a routine, two-paragraph statement that didn't mention Metro.

"The programs that you mentioned are just a fraction of the hundreds of programs that are being reduced nationwide so that the government can begin living within its means just like every American family and business is doing. We have to get serious about our fiscal situation," said Cantor's spokeswoman, Laena Fallon.

Metro is the core of our region's overburdened transportation network. Its success is crucial to controlling congestion, curbing pollution and absorbing new residents.

Not all government spending is poisonous. Even a conservative like Bob McDonnell sees that. This is no time for Congress to back away from its long-term promise to help the Washington region restore quality public transit.