The Republican Party’s socially conservative base, conflicted for months over which presidential candidate to back, is increasingly coalescing behind Rick Santorum in a shift that some observers say may energize his bid and slow Mitt Romney’s momentum toward the nomination.

Santorum, a former Pennsylvania senator, collected no delegates when he swept a trio of Republican contests Feb. 7, yet he demonstrated his growing popularity among voters who make opposition to abortion rights and gay marriage a priority.

These voters — galvanized by opposition to President Barack Obama’s decision last month to mandate that religious employers include birth-control coverage in their health plans – – are becoming more motivated to back Santorum in an effort to draw the starkest possible contrast with the president.