President Obama must be tempted to respond to his progressive critics with a quote from the old-school rapper Kool Moe Dee: “How ya like me now?”Repeal of the military’s bigoted and anachronistic “don’t ask, don’t tell” policy on gays in the military a campaign promise that seemed to be slipping out of reach doesn’t fully mend the relationship between Obama and the Democratic Party’s liberal wing. But it’s a pretty terrific start.Progressives needed a clear, unambiguous victory to ease the sting of those extended tax cuts for the rich. They got one on Saturday with the Senate’s historic vote to end “don’t ask, don’t tell” and Obama won vindication for the slow, patient, step-by-step approach that drove gay and lesbian activists crazy but ultimately produced a stunning result.Administration officials believed from the beginning that getting the discriminatory policy repealed, and allowing homosexuals to serve openly in the armed forces, would require getting the Pentagon brass on board. The military leadership had to support the change, or at least accept it. Otherwise, repeal-minded members of Congress might balk at casting a vote that could be portrayed as somehow weakening America’s defence.So the White House spent months demonstrating that Defence Secretary Robert Gates fully endorsed the end of “don’t ask, don’t tell” and that the service chiefs would implement the change. A key part of this painstaking strategy was the Pentagon’s 10-month study of the impact of eliminating the policy which concluded, essentially, that there was likely to be no adverse impact at all.The study included a military-wide survey, which found that two-thirds of service members believed ending the policy would have positive, mixed or neutral effects. Perhaps more significant was the study’s description of the experience of the British, Canadian and Australian militaries, which changed their rules and allowed gays and lesbians to serve openly. What happened? Nothing at all.“Uniformly, these nations reported that they were aware of no units that had a degradation of cohesion or combat effectiveness, and that the presence of gay men and lesbians in combat units had not been raised as an issue by any of their units deployed in Iraq or Afghanistan,” the study reports. None of those other nations had problems with recruiting or retention, either. The change turned out to be a non-issue.Opponents of ending “don’t ask, don’t tell,” including Sen John McCain, had insisted that Congress not act until the Pentagon study was completed. When it finally came out, they promptly began moving the goalposts, demanding yet more hearings and testimony. It looked as if they were going to run out the clock and leave the issue for the new Congress, which will be far more conservative.But then Joe Lieberman and Susan Collins came to the rescue.I’ve been sharply critical of Lieberman in the past, and I suspect I’ll have occasion to be equally critical in the future. But on “don’t ask, don’t tell,” he was pure gold. Sometimes it seems as if Lieberman, who serves as an independent, delights in driving liberal Democrats crazy, but on social issues he still has a righteous sense of fairness and justice. His well-established record as a hawk on military matters gave him the credibility to push this change and push it he did, even when all seemed lost.And as for Collins, I’ve wondered how she can be called a “moderate” when she reliably stands with the archconservative, down-with-the-president GOP leadership in the Senate, especially on important procedural votes. But she was brave and principled on “don’t ask,” and by linking arms with Lieberman she allowed seven other Republicans to cast their votes on the correct side of history.Now that Congress has acted, the military will move with caution to implement the change. Judging by what has happened in other countries that took this step, however, the process will probably move much faster than anyone expects. A year from now, we’ll all be wondering what the big deal was.For gays and lesbians currently serving in the military, this doesn’t mean they necessarily have to make public their sexuality. It just means that soon they won’t have to fear being discharged for being who they are.And for President Obama and the left, this is an important milestone a reminder that even in dysfunctional Washington, what Sarah Palin derided as “that hopey-changey stuff” can still produce real hope and change.lEugene Robinson’s e-mail address is eugenerobinson@washpost.com.(c) 2010, Washington Post Writers Group