Leading article: A treaty that tests mutual good faith

Although voters gave the Democrats a mauling in the US midterm elections, the dog days of the current Congress are not turning out too badly for Barack Obama. Fresh from his success in the repeal of "Don't ask, don't tell", he looked set yesterday for a second Senate victory: ratification of the new Strategic Arms Reduction Treaty (Start) with Russia. It is an achievement that is just as important, but in a very different way – not only because the necessary two-thirds majority would be far harder to achieve in the new Congress.

No one pretends that the sort of nuclear warhead counting enshrined in this treaty is anything like as crucial as it was in the Cold War years. Nor can it really be said that the past year, which followed the expiry of the old Start treaty, has been more dangerous for US-Russia relations than the previous one; the leaders of both countries made sure that it was not. The difficulty was rather the message sent by America's non-ratification.

Almost two years of effort by Mr Obama to "press the reset button" with Moscow would have come to nothing. Both the US President and his Russian counterpart, Dmitry Medvedev, would have looked foolish for investing their political capital in so risky a proposition. The domestic standing of both – but especially of Mr Medvedev – would be weakened, and the prospect of warmer East-West relations generally would fade.

It was shrewd US diplomacy that placed a new Start treaty at the heart of Mr Obama's Russia policy; arms control remains familiar territory for the post-Soviet Kremlin. And while the weapons reductions may help make the world a safer place, passage of the treaty was always regarded by the Russians less as a security requirement than a test of US good faith, and a condition for further progress.

Assuming no last-minute hitches, ratification of Start also shows how the novice Obama White House is learning to deal with Congress. In stressing the security value of the treaty, it took the argument to the Republicans, casting nay-sayers as poor guardians of US interests. This savvier approach should stand the President in good stead when he faces a more hostile Congress in the new year.