COLUMBIA, S.C. -- With the South Carolina Republican presidential primary a week away, former Sen. Rick Santorum on Saturday received the endorsement of 150 influential Christian conservative leaders who are hoping to prevent former Massachusetts Gov. Mitt Romney from becoming the GOP nominee. The group, suspicious that Romney's commitment to social conservative causes such as ending legalized abortion is weak, met at a ranch outside of Houston, Texas, in hopes of rallying around one candidate rather than split their votes among three - Santorum, former House Speaker Newt Gingrich and Texas Gov. Rick Perry. The endorsement came as the Republican...