Are just that. That's why we have elections and don't choose Presidents from polls.
1980. Similar economic climate, many many many problems. Carter, who had beaten a republican incumbent, albeit not an elected one (Ford), got crushed in 1980 in spite of pre election polls to the contrary. Reagan was not that popular until voting day. Like Romney, Reagan had lost the nomination in prior elections (2 actually for Reagan).
Check the poll numbers from Gallup site pre-election 1980. It can happen. Just sayin.
Late Upsets Are Rare, but Have Happened