The Senate's adoption of the Lieberman/Kyl amendment designating Iran's Revolutionary Guard a "terrorist group" isn't merely embarrassing, it's counterproductive. Designating the Revolutionary Guard a terrorist group -- which in contemporary American terms means they're a target -- makes it all the more important for Iran to keep us tied up and weakened in Iraq. The more we telegraph that we'd like to devote forces to regime change or strikes in Tehran, the stronger Iran's incentive to keep Iraq an unstable morass trapping ever-greater numbers of American troops who can't be easily diverted from a chaotic mission and are geographically vulnerable to Iranian counter-attack.
Additionally, it further ensures Iran's incentive is to keep Iran from becoming stable under American protection and thus a platform from which we can safely launch attacks on the Iranian state. Iran will never allow Iraq to stabilize so long as Iraqi stability degrades the safety of the Iranian regime. And given that Iraq is Shi'ite, Iran is Shi'ite, and America is not, Tehran's got a whole lot more pull there than we do. So not only is the Lieberman/Kyl amendment bad policy vis-a-vis Iran, but it's terrible policy for stabilizing Iraq -- which Lieberman professes to care about. "Professes" being the key word there.