前参议员桑托勒姆第二次竞选总统争取共和党提名

White House on Wednesday, joining an already crowded field seeking the 2016 Republican presidential nomination.

The 57-year-old Santorum will make the announcement at a manufacturing plant in Pennsylvania, the state he represented in both the House and Senate for several years from 1991 until 2007, when he lost his Senate re-election bid.

Santorum was little regarded when he launched his first bid for the Republican nomination in 2012, but stunned political observers when he narrowly won the influential Iowa party caucuses over Mitt Romney, drawing supporters attracted to his strong social conservatism. Santorum went on to win 10 more state caucuses and primaries before his campaign lost momentum to Romney, the party's eventual nominee.

Despite his strong showing in 2012, Santorum faces another uphill battle in the upcoming race, with well over a dozen candidates who have either formally entered or are considering entering the race, including former governors Jeb Bush and Mike Huckabee, current senators Rand Paul, Marco Rubio and Ted Cruz, and retired surgeon Ben Carson, many with strong social conservative credentials.