Barack Obama’s and John McCain’s campaigns are both pushing rosy scenarios for Tuesday’s vote. But only one can be right.

Obama’s strategists believe their candidate continues to enjoy not just a sturdy lead in national popular opinion — at least 5 points in most polls — but, more importantly, advantages in states George Bush won handily, such as Colorado and Virginia. Democratic strategists believe that whatever surprises Election Day may hold won’t be sufficient to knock Obama off his path to victory.