Who is legitimate?

The last couple of weeks, Republicans have raised one big question about Barack Obama: Who is he?

Governor Sarah Palin has pushed the point, saying bluntly that the Democratic presidential candidate has palled around with terrorists.

The pushback has been fierce, with some civil rights leaders accusing the Republican ticket of “playing with fire.”

It’s perfectly appropriate, of course, to ask questions about Obama’s experience and his plans for America, should he win office.

But this looks more like tribal politics. and Americans should reject it forcefully.

Which isn’t to say that Obama is the better candidate, or should win.

Perhaps McCain is more qualified, or has better ideas for leading the nation — or seems more sympathetic to the country’s pressing needs.

But whenever one politician tries to delegitimize another, it should raise alarms.

It’s one thing to out-argue, or out-think. But to suggest that another candidate is somehow dangerous or suspect — that’s simple demagoguery.

When participants at Republican rallies accuse Obama of “treason,” or pray for a “Christian” victory over the Democrat, or accuse him of being a terrorist, McCain and Palin had a choice.

They could repudiate that kind of rhetoric, in blunt terms; or they could listen and nod, suggesting a silent complicity. Too often, they chose the latter course.

Whether he likes it or not, John McCain is fighting for the presidency at a historic time.

First, America faces a monumental crisis, economically and in our civic institutions. We simply cannot tolerate more divisiveness.

Second, McCain faces the first African American candidate with a significant chance of winning the White House.

In a society where race has divided us for centuries — and where many of the great black leaders have been murdered — that raises the bar dramatically.

In the end, Senator McCain — an honorable man, who has served his country for decades — should keep one thought in mind.

If he and his proxies continue their attempts to disqualify Barack Obama, he may find his own legitimacy in tatters.