I think it was Wallace Stevens who wrote, "If sex were all/ then every shaking hand/ could make us squeak, like dolls, those wished-for words." (This is from memory, so I may be off.) Character in politics is like that: both essential and terribly insufficient to answering the indispensable questions. I share the sense that Bradley and McCain exude an almost gravitational energy by virtue of speaking plainly. Yet that we even imagine this to be enough shows how thin our political hopes are. Character sometimes precedes (but does not always accompany) good policies, but politics in the narrow electoral sense is mainly about policies, and the obsession with personality reflects how little hope we put in policy.
Also, sincere people have done enormous harm in the last century, and throughout history. The blood-soaked past that you evoke has sincerity among its leading consorts: fascism, crusading fundamentalism, totalitarian socialism, revolutionary zeal. Irony at its best goes back to the Socratic insight that our greatest and most ennobling passions can't be consummated in the world, and so disciplines those passions in a way that enables them to live in the world. This kind of ironic commitment to politics is probably the kind we should want. In the last chapter of the book I mean irony not to be banished by commitment, but tempered and made more compatible with work and feeling. Many people achieve just this combination. I was not making a novel suggestion, but just honoring people who've done something admirable with themselves.
To your point that people are pretty satisfied with the present state of things: yes. The basic human relationship to politics is the desire to be left alone. It's not our only motive, and the argument of the book is that we can't afford to act as if it were; but ignoring it and wishing we were all devoted and upright yeomen is just willful naiveté--which deserves ironic dismissal, at the gentlest.
So a word on what the book endorses. First, an idea of politics, or of public work, that is broadened past elections to contemplate how we do our work, how we relate to our families and communities, and also how we vote. Second, an effort to integrate our private and public motives to some extent--to connect careers with commitments, to work to preserve or make available to others what we love in our own lives. Third, a willingness to speak, more than we do, about these commitments, and admit their place in our decisions. Last, a skepticism keen enough to serve as a stay against mawkishness and gullibility. None of this is original. All of it is present all around us. It seems to me to be worth honoring explicitly and considering more clearly than we do.
It is a premise of the book that how we think about things is an eminently practical matter, redounding to all our decisions. That is why an exercise in public thought seemed to me a worthwhile risk.