A study of the last five town hall style presidential debates has found that journalists moderating the events choose liberal questions over conservative questions by a two-to-one margin, a result that has Romney campaign bracing for a biased debate tonight.

Ideologically left questions outnumbered conservative questions 28 to 14 at the debates from 1992 to 2008, according to the conservative media watchdog group Media Research Center.

All eyes will be on CNN's Candy Crowley as she decides which questions from the audience of undecided voters in liberal New York to pick when Mitt Romney and President Obama face off at 9 p.m.

Only once, when ABC's Charles Gibson moderated the 2004 town hall, were Democratic- and Republican-leaning questions equal in number.

"But Gibson is the lone exception," said MRC's Rich Noyes. "The other journalists who have moderated these forums -- ABC's Carole Simpson in 1992, PBS's Jim Lehrer in 1996 and 2000, and NBC's Tom Brokaw in 2008 -- all favored liberal agenda questions as they chose which of the undecided voters would actually participate in the debate."

In a warning to Romney, he added, "if history is a reliable guide, Mitt Romney has twice the chance of facing a hostile liberal question Tuesday night as Barack Obama has of facing a question based on a conservative agenda, as the record shows a 2-to-1 tilt to the left in past town hall debates."