Cowardice isn't limited to just Democrats, though I think you're generally right - Dems have more than their fair share.
Grace under extreme pressure is an undefinable quality....you either have it, or you don't. And either way, it's easily apparent to others whether it's there or not.
For instance, I'm in IT and my company recently had a serious (read: company-threatening) computer issue. The boss, who generally is a really nice guy and excellent to work for, was completely paralyzed by indecsiveness. His second in command took a powder (went on vacation for the week, and the boss let him!!!), so the whole thing was dumped on me. I worked with the vendor - the Boss "made the decisions", but was really following our advice - and we muddled through. I'm still drawing a paycheck, so I guess I did something right.
However, the Boss is already out the door, and the 2nd in command will be following shortly. When the chips were down, they just weren't capable of making the decisions that needed to be made.
Now, if we screwed up, it would have meant the end of work for a bunch of people. Inconvenient, but certainly not life-threatening. Contrast this with the life and death decisions that this captain had to make. I've no idea how this particular captain didn't get weeded out - at some point in his career, he must have been put in an all-in type situation.
Some people just keep getting lucky... until their luck finally runs out.