Why would it be a bad thing for democracy if a new Not-Romney swept in on the Republican convention, captivating the delegates and capturing a majority of their votes?

The most important reason is that anyone who jumps in at that point will have bypassed six months' worth of opportunities to meet voters and be chosen or rejected by them. The voters are speaking primary by primary, caucus by caucus and, like it or not, the party brass must listen to them. Party leaders can't just set aside the will of the people just because they don't like the result. You expect that sort of tactic in places like North Korea, Belarus, Moldova, Burma, maybe Laos, but not the United States, paragon of democracy.

A dark horse candidate might generate excitement for a while, certainly at the convention and in the media, but when the excitement wears off, all those people who voted for Mitt, Rick, Ron or Newt will mull it over and start feeling a bit resentful. Anyone who donated to their campaigns will feel resentful. And surely some of those resentful people will feel that their democracy has failed them and, when election day arrives, decide not to vote at all.

Other important qualities of a candidate are tested by the rigor of a primary campaign as well. We've seen a series of Not-Romneys bite the dust so far this season. If a candidate has skeletons in his or her closet, they are quickly exhumed and brought out for public inspection. If they are found to be unbecoming of a President, that person is out. A dark horse candidate would ride in so quickly that there would be no time to poke around in his closet... by the time the dust clears he'd be the nominee and it would be too late.

If a candidate does not have the requisite mental agility to hold his or her own in conversation, that person is out too. The debate skills of a dark horse candidate would not be tested until he or she came face to face with Obama in the real race. And not only mental agility is revealed by debates, but mental content as well... candidates likely don't even have all their views on every issue thought through at the beginning of a primary season, but by the time they've been through a series of debates, their own ideas have crystallized, their style matured, the voters seen them grow into the role of a real contender. Those things aren't just niceties - they matter.

On a larger scale, the fact that the Republican party is having so much trouble rallying around a candidate this year means something. You can't just cover that up with a band-aid and hope it goes away. They need to sort out what their own identity is - one party or two? Maybe three? Does being "conservative" mean they can't adapt to the changing demographic realities of the United States? The factions within the party must either be resolved or, perhaps, marginalized into a new party of their own, in order for the party as a whole to continue to evolve for the 21st century. A dark horse candidate would certainly speed up that process, but in doing so would bring us to the brink of betrayal of the very principles of democracty that our country is founded upon.