Santorum - For Whom the Bellwether Tolled

As older Republican primary voters go, so went Rick Santorum's presidential campaign.

Santorum, who suspended his campaign Tuesday by conceding the "race for us is over," did well in primary states only when he did well among voters 50 and older - especially voters on the cusp of retirement age.

According to the exit polls, Santorum's finishes in individual primaries almost always mirrored how he did among voters aged 50 to 64. He took his biggest shares of 50- to 64-year-old voters in Alabama, Iowa, Louisiana, Mississippi, Oklahoma and Tennessee -and won them all. And where he came in second among 50- to 64-year-old GOP primary voters - in Arizona, Illinois, Maryland, Massachusetts, Michigan, Ohio, and Wisconsin - he finished in second place. And where he came in third among 50- to 64-year-old primary voters - in Florida, Georgia, South Carolina, and Vermont-he finished third.

Santorum never seemed to break through with Republicans aged 65 and older, a bracket that his chief rival, Mitt Romney, seemed to lock down in state after state. In Ohio, for example, which was as close to a squeaker as any GOP primary this year (Romney, 39.7 percent; Santorum, 37.1 percent), Romney walloped Santorum by 16 percentage points among voters 65 and older. - Susan Milligan