ANALYSIS: Hiss by Democrats sign of challenge for Bush.

Byline: Jim Puzzanghera

Feb. 3--WASHINGTON -- The standard responses from members of Congress during the president's State of the Union address usually follow a graduated scale of support: from stone silence to polite applause to standing ovation and, finally, the occasional enthusiastic, "hurrah!"

But as President Bush laid out his case for overhauling Social Security on Wednesday night -- an initiative that by all accounts will require bipartisan support to get accomplished -- he managed to earn a rare response from Democrats that did not bode well for his plans.

They hissed.

Their reaction came when Bush asserted that Social Security is "headed toward bankruptcy" -- a point that most Democrats and some analysts dispute.

"When you start out by stating a premise that's factually …