Bearings are the calculations a navigator makes to stay on course. “Losing your bearings” means, essentially, losing your compass — going off course.

When Obama last night suggested that McCain was “losing his bearings” in suggesting that Obama was in cahoots with Hamas, the choice of words was provocative, sure. Obama was saying that McCain presents himself as an unconventional high-road politician, but here had instead taken a low potshot. He’d lost his moral compass.

Here are Obama’s words:

“This is offensive, and I think it’s disappointing, because John McCain always says, ‘Well, I’m not going to run that kind of politics.’ And then to engage in that kind of smear, I think, is unfortunate, particularly since my policy toward Hamas has been no different than his,” Obama said.

The Illinois senator added: “For him to toss out comments like that, I think, is an example of him losing his bearings as he pursues this nomination. We don’t need name-calling in this debate.”

But the McCain people’s charge that it was a cheap shot about the candidate’s age suggests that they have, um, further lost their bearings.

Now, if Obama had said “McCain has lost his marbles”? Yeah, that might’ve been a comment about age. And — since “bearings” also has another meaning, for mechanical parts that are similar to, er, marbles — maybe there’s even a little bit of a taunt behind the word choice, an extremely subtle reference to McCain’s reputation for sputtering anger. But that’s not what the McCain people are complaining about.

With one campaign organization on guard against racial digs and the other defensive about age-ism, it’s going to be a fun election season!