Will the Stars Wars system work?

Democrats have argued for decades that missile defense cannot possibly work.  On the other hand, if that were really the case, how do you explain the Russian reaction to the system?  From the (UK) Telegraph:

A top Kremlin official has told the United States Russia wants "red button" rights to a new US-backed missile defence system for Europe, a move that would allow it to influence the shield's day-to-day operational use.

Sergey Ivanov, Russia's deputy prime minister, made the controversial demand during a visit to the United States where he met with top officials including Hillary Clinton, the US Secretary of State.

"We insist on only one thing," he said of the nascent US-backed missile defence shield. "That we are an equal part of it." [Emph. added]

Separately, Haaretz reports on successes with the first operational use of Israel's iron dome missile defense system:

As the rocket fire from Gaza on southern Israel continued Friday, the Iron Dome missile intercepted three Grad rockets that were fired toward Ashkelon.