Count this as the most under-covered story of the week: late Thursday, Republicans in the House of Representatives forbade a vote on a resolution that would end the war in Afghanistan next year—because they knew it would pass. This means that, though we don’t have the roll call vote to prove it, Obama’s current strategy for Afghanistan is no longer sustainable in Congress.

You might recall that last year, Representative Jim McGovern offered an amendment to the defense authorization bill that called for President Obama to offer an “accelerated” withdrawal plan to Congress—which lost by only eleven votes, 215-204. All but eight Democrats supported it, along with twenty-six Republicans, including key members of the House Armed Services Committee.

Yesterday, McGovern was back with another amendment that would require the end of combat operations by the end of 2013—a year ahead of the president’s schedule—and redeployment by the end of 2014. It would require Congressional authorization for any deployment of troops to Afghanistan after 2014. McGovern’s bill was bipartisan and co-sponsored by Representatives Ron Paul, Walter Jones and Adam Smith, and had the full support of the Democratic leadership in the House.

But Republicans on the Rules Committee didn’t allow it to come for a vote—and two GOP sources told CNN the reason was that “Republicans were concerned the amendment could pass.” They expected a significant bloc of Republicans to support it, and that “they couldn’t rely on the White House to lobby Democrats against it.”

Instead, Republicans only allowed debate on a resolution by Representative Barbara Lee, which would have effectively ended the war immediately by only authorizing further money for withdrawal efforts. That has no real chance of passing the House.

McGovern, speaking on the House floor, was incensed. “What is the Republican leadership afraid of? Are they afraid a bipartisan majority of this House will vote to follow the will of the American people and change our Afghanistan policy?” he asked.

The vote would have been a massive embarrassment for the White House, coming as NATO leaders are gathering in Chicago this weekend to discuss the war strategy. Republicans rarely miss a chance to embarrass the president, but party leaders—including Mitt Romney—have long supported the war and have at times criticized Obama for drawing down even on his longer timetable.

But this should still be a huge story, particularly for reporters covering the summit in Chicago this weekend. Backed by constituents that are sour on the decade-long war in Afghanistan, Congress no longer has the votes to support the president’s plan.