The polls show Park with an imposing lead- is this still true on the ground?
Recent polls are quite close, with Park holding a narrow lead over Moon (44 to 40 in the poll linked below). Ahn has dropped out of the race, so the risk of vote-splitting on the left has been averted (though Ahn was more electable than Moon, so this is sort of a wash--pretty sure Ahn would have won in Park v. Ahn, but in Park v. Moon I think Park wins).
http://www.bloomberg.com/news/2012-11-25/korea-s-park-moon-register-for-election-after-ahn-quits-race.htmlThis is also way closer than a hypothetical two-way Park-Moon race was polling back in the summer, when Park usually had a large double-digit lead on Moon even without Ahn in the race.