Presidential Race

Does it seem like the party running against an incumbent President often chooses a candidate that is highly unlikely to win?

Bush vs. Kerry

Clinton vs. Dole

Reagan vs. Mondale

Nixon vs. McGovern

Obama vs. Romney(?)

Is there any dispassionate, unbiased person out there who honestly believes that Kerry, Dole, Mondale, McGovern, or Romney had/have a chance to win unless the incumbent was exposed as a cross-dressing child pornographer shortly before the election?  Kinda makes one wonder what is going on in the primary election process that arrives at these candidates.  

 There are several possibilities:
1) The opposing (to the incumbent) party may have decided that it is impossible to unseat the incumbent short of a miracle, so the selected candidate is sacrificial fodder.  This seems unlikely due to the gargantuan egos and incredible work involved, but the slate of Bozos the Republicans have fielded for this election certainly brings the possibility to mind.
2) The opposing party may be manipulating the primaries so that a powerful candidate (within the party) is selected at a time least likely for success.  This might be done to push aside the candidate in the future so a more desirable candidate is selected for a more winnable election.  This too seems unlikely because it implies a secret, well-coordinated, focused effort within the party hierarchy.  Neither secrecy, nor coordination, nor focus are hallmarks of any actions within our political system.
3) The media might be manipulating the outcome by coverage patterns for certain candidates in order to steer results toward their favored candidate.  While I believe the media does a disservice to the public in their coverage, I don't believe they are capable of a successful overt effort to steer the election for the same reasons as the parties being unable to steer it.
4) The primary process is actually what it seems to be.  While severely disconcerting, this seems to be the most likely situation -- Heaven help us!