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Rick Santorum has considerable momentum entering the Iowa caucuses, and should he become the GOP's presidential nominee, Democrats will have plenty of things to say about him. His willingness to bomb Iran and his conservative social views are enough to rally the liberal base.

Two attack ads aimed at Santorum during his 2006 Senate campaign, however, offer a glimpse at how Democrats could attack him in 2012.

Santorum's  2006 re-election bid was almost over before it started, so the lessons may be few. The two-term incumbent trailed his Democratic opponent by large margins for most of the race, and Bob Casey (D), now Pennsylvania's senior senator, led Santorum in every major poll from February 2006 until Election Day.

Santorum recently explained his 18-percentage-point loss as a symptom of the 2006 Democratic wave. "It was the worst election year for Republicans in the history of the state," he told ABC's Jake Tapper on Monday. "We stood up and didn't flinch. We stood up and said, This is what we believe the problems are. Social Security reform: not a popular thing. Iraq, win the war: not a popular thing."

Democratic groups didn't do much campaigning against Santorum. The Democratic Senatorial Campaign Committee, for instance, didn't run a single ad attacking him.

But Casey's campaign did run these two ads attacking Santorum. The first took aim at Santorum's support for President Bush's failed effort to privatize Social Security; the second points to his 2005 book, "It Takes a Family," and accuses Santorum of dismissing the economic struggles of two-income households.