According to a new Public Policy Polling survey, Democrats are poised for a decisive victory in tomorrow’s special election to replace Gabby Giffords.

The poll shows Democrat Ron Barber leading his Republican challenger Jesse Kelly by a 53 to 41 percent margin. Green Party candidate Charlie Manolakis is polling at 4 percent.

Barber leads 58 percent to 37 percent among the 57 percent of voters who have already cast their ballots; that massive 21 point edge suggests that Barber is almost guaranteed to win on Tuesday.

Although Barber is comfortably ahead in a relatively conservative district — John McCain won there by a 52 to 46 percent margin in 2008 — there are signs that President Barack Obama may not fare as well in November. Only 44 percent of voters in the district approve of Obama, compared to 50 percent who disapprove. Furthermore, despite Barber’s 12 point lead, likely voters only say that they want Democrats to have control of Congress by a 48 to 44 percent margin. As PPP notes, “That’s an unusually large gap between the horse race and who voters want to have control.” It seems that Barber’s personal popularity — he has a 58 percent favorability rating — and his close ties to the immensely popular Giffords are overshadowing voters’ ambivalence about the Democratic party.

“Democrats are likely to win this race comfortably tomorrow,” said Dean Debnam, President of Public Policy Polling. “But the unusual circumstances of the contest make its relevance to any other contest later this year pretty limited. It’s not often you have a special election to replace an incumbent who resigned with a 67% favorability rating.”