Donald Trump should pick Rick Santorum as his Republican vice presidential running mate because the former Pennsylvania senator "would unite the establishment wing of the GOP with the conservative movement," conservative activist Richard Viguerie said Friday."Neither of these two major wings of the party could claim that Santorum as the VP pick would be a disaster," Viguerie said in a blog on his Conservative HQ website. "With all his qualities, he bridges the often-wide gap between the leaders of the GOP establishment and the conservative movement."For Trump, who has given both the conservative movement and the GOP establishment cause for concern, Rick Santorum is almost uniquely suited to help soothe both factions in ways that would help defeat Hillary [Clinton]."Santorum, 58, dropped out of the 2016 race in February. He ran in the 2012 primary, finishing second in delegates after eventual nominee Mitt Romney. He ran on a conservative pro-life platform that appealed to evangelical voters.He served in Pennsylvania Senate from 1995 to 2007 and had served as chairman of the Senate Republican Conference.Santorum endorsed Trump's candidacy last month, citing the presumed nominee's list of possible Supreme Court candidates. Santorum had supported Florida Senator Marco Rubio after he quit the race.According to Viguerie, Santorum would "as no other candidate except Ted Cruz, help Trump complete the circle necessary to build a winning populist-conservative coalition by bringing culturally conservative pro-lifers into the fold."He knows Washington and Capitol Hill and certainly after his strong run in 2012 and his leadership in the Senate 'could be viewed as somebody who could be president,'" the columnist said.Viguerie called the senator "my conservative dark horse" — adding that "putting a candidate on the ticket so clearly identified with the pro-life cultural conservative agenda would do more than merely placate conservatives as the old rules of vice presidential selection would dictate."Rick Santorum is clearly 'one of us' — a long-time movement conservative — and it is hard to imagine pro-life cultural conservatives not backing a Trump-Santorum ticket."