You might not think Senators John McCain and John Kerry have all that much in common. McCain is a Republican, Kerry a Democrat. McCain is in the midst of the race for the 2008 Republican nomination for President, while Kerry—the Democratic nominee—is dead in the water when it comes to a future run. McCain made his bones on the “Straight Talk Express” in 2000 even as Kerry dissembled like a French semiotician in 2004.

But McCain and Kerry, both Vietnam War heroes, have more in common than you might think—including an ability to self-destruct when it counts most.

Kerry first. All JFK had to do in 2004 was to be true to his roots as an anti-war candidate and to take on the Iraq War before it became the flavor of the month to wax doubtful. Instead, the best Kerry could do was spend the entire campaign explaining why he had to vote for the $84 billion before he voted against it. By taking such a stand against the war based on conscience, Kerry still might have lost, but is there any doubt he could have bounced back in 2008 as the Iraq conflagration went south and turned sour?

Now McCain. Did somebody say “Straight Talk Express” or even “maverick”? McCain is now anything but a Republican renegade, sinking in the polls faster than you can say “counter-insurgency.” Rather than speaking from the heart, the very senior Senator from Arizona has been busy talking out of both sides of his mouth to reassure the conservative electorate that he is one of them—even though he clearly is not.

He spoke at Bob Jones University to assuage the Fundamentalist Christians and at the Discovery Institute to stroke and to stoke the creationists. Does he believe in such poppycock? Absolutely not. But like Kerry, McCain is pandering to causes he embraces only so as to be elected.

And that is ultimately going to cost him any chance of being President. McCain is sinking in the polls against uber-Mayor Rudolph Guiliani because of (a) his unbending stance on Iraq; and (b) his advance age of 73 and counting. Instead of sticking to his guns—and yes, maybe even losing—John McCain, like John Kerry before him, has tried to find a course (if not a cause) that would get him elected.

Both McCain and Kerry could have done far better by being the best they could be, even if it meant an unpopular stand or three. Like McCain, Hillary Rodham Clinton faces the same demons of accommodation when it comes to her refusal to admit any “mistake” about the war in Iraq. She is likely to achieve the same unhappy and unavoidable result.

Ambition is a wonderfully horrible thing, and it trumps values in American politics every time.