A minor but crucial hurdle for the START treaty was cleared in the Senate on Saturday, as the chamber voted not to adopt an amendment written by Arizona’s John McCain. The fix, which would have removed language that links offensive and defensive weapons, would have caused the Obama team to go back to Russia to renegotiate the final wording of the treaty. Now, the Senate is ready to start debate. They’ll need two-thirds of the chamber to ratify START, meaning 67 votes if all 100 senators are present. All Democrats are expected to support the treaty, but it’s unclear if they’ll be able to win enough Republican support to clear the threshold.