Of course, the selection of Sarah Palin as his running mate belies the claim of a maverick who puts country over politics. The choice of Palin can only be seen as a political stroke, designed to inspire the right-wing evangelical base of the party that had been notably skeptical about McCain. Given her zealous and extreme fundamentalist positions, she won't win many Hillary votes -- that was always a ruse -- but she will galvanize the evangelical right for McCain. It is clear that the man who hectors constantly that the war against terror is the "transcendent challenge of the 21st Century" just made a choice that placed his political needs over what he considers the central national mission.

But, this isn't an aberration. McCain has flip flopped on many positions -- supporting Bush's tax breaks after opposing them, catering to the right on immigration after resisting them, embracing Jerry Falwell after condemning him -- in pursuit of his party's nomination.

For an old Washington hand, none of this is surprising. McCain has been in Washington for over a quarter century of compromises and dealing. The question always for career politicians is what is left of their character? Are there any core beliefs that are not for trade or for sale?

What is left for John McCain? The formative experience of McCain's life -- as he reminds us regularly -- was the time he spent as a POW, surviving terrible torture. That experience no doubt led McCain to lead the effort to enforce the Geneva Conventions' ban on torture on the Bush administration in the wake of Abu Ghraib, Guantanamo and the CIA's rendition operations. In pushing to make the military's code of conduct the law of the land, McCain not only stood for the best of America's tradition but also was expressing the core of his own personal experience.

He had the votes to defeat the president on the Military Commission Act in 2006. And then he gave it away. Faced with the reality that enacting a ban on torture would cost him politically in the Republican Party, McCain surrendered. He signed on to a "compromise" bill that left the President to determine, in his sole discretion, which interrogation methods did or did not comply with the Geneva Conventions' provisions. He empowered the president to define what constituted torture. He simply surrendered on this core issue. For the best treatment, check out Glenn Greenwald here.

Now in Washington, politicians are constantly faced with the need to compromise. You give up something to make some progress. You vote for bad bills in order to placate powerful local interests. You decide which battles you can fight, and duck the others. That makes any politician vulnerable for criticism, but is part of the business.

But every leader must have a set of principles that can't be compromised -- otherwise everything is transactional, everything for sale. When McCain is willing to sign away the principle derived from what is the defining moment of his life, then the question is what core of character remains?

We've seen this before in powerful leaders. Colin Powell, for example, was formed by his experience as a young officer in the Vietnam War. He -- and others -- vowed that never again would they allow US troops to be led into war without adequate preparation, a clear mission, an exit strategy. It became known as the Powell doctrine. As Secretary of State, Powell faced many issues where he was rolled or ignored by the neo-cons around Dick Cheney who were driving the policy. He chose to stay and fight for another day. But on Iraq, he had to know that the mission was false, the force inadequate, the plans for exit unclear. And he had the power to stop the war if he had chosen to go public and resign. Instead he chose to stay at the table, to fight the future battles. In doing so, however, he gave away the central core belief of his career. After that, anything is negotiable.

That's where we are with McCain. The pursuit of the presidency is a powerful thing. The Republican Party, so captured by the far right, a difficult terrain to traverse. To win the nomination, he was prepared to give away even his core. Politics came not just before country but before core conscience.

So when Davis says the election isn't about "issues," or presumably the conservative record of failure, but about character, he is peddling McCain's message, but exposing his tragic weakness.