For many Americans, the measure of a candidate seeking the presidency comes down to questions of character.

Perhaps the most important of these is: How does he or she react under pressure?

It is certainly reasonable to surmise that, if a candidate cannot handle the rigors of the campaign, then he or she might have trouble tackling the responsibilities of the office.

It is this fair test that John McCain has, in recent days, been failing – badly.

There is no question that McCain has been hit hard by the success of Barack Obama’s trip to Afghanistan, Iraq, the Middle East and Europe.

After essentially demanding that Obama make the trip — with the implicit suggestion that the presumptive Democratic nominee for president was not up to the challenges of the international stage — the Republican candidate and his supporters then whined about the fact that the media was paying attention to Obama’s travels.

As it turned out, McCain was right to worry that reporters, and by extension the American people, would be paying close attention to Obama’s global tour.

The Democratic candidate went from strength to strength, He focused attention on the mess that the Bush administration has made of Afghanistan, advanced the discussion of how and when to withdraw U.S. forces from Iraq, met with both Israelis and Palestinians on a successful transit of the Middle East, earned not just respect but encouragement from world leaders, consulted knowledgeably with U.S. generals and enjoyed the cheers of troops who treated him as their next commander-in-chief.

Desperate to find something to complain about, McCain seized on the fact that Obama did not visit wounded U.S. troops at Ramstein Air Base in Germany.

The McCain camp has even gone so far as to suggest that the failure of the Democratic candidate to use wounded troops as the backdrop for a campaign-style visit to Germany “casts serious doubt on his judgment and calls into question his priorities.”

So what does U.S. Sen. Chuck Hagel, a Nebraska Republican who served in Vietnam, say about the latest spin from McCain, the man he actively supported for president in 2000 and who he continues to describe as “a very dear and close friend of mine”?

Hagel, who accompanied Obama on the visits to Iraq and Afghanistan, was asked on the CBS program “Face the Nation” about the German leg of the Democrat’s globe trot.

“At that point, it was a political trip for Senator Obama,” Hagel explained.” “I think it would have been inappropriate for him (to visit the hospital) — and certainly he would have been criticized by the McCain people and the press and, probably should have been — if, on a political trip in Europe, paid for by political funds, not the taxpayers, to go essentially then and be accused of using our wounded men and women as props for his campaign.”

Of course, Hagel is right.

McCain and his aides were so desperate to find something to complain about that they would have attacked Obama no matter what he did.

But the nature of this attack, and of the broader suggestion that Obama is somehow unconcerned about the United States and its troops, reveals the real McCain.

As Hagel says, “I think John is treading on some very thin ground here when he impugns motives, and when we start to get into ‘You’re less patriotic than me, I’m more patriotic.’ John’s better than that.”

Unfortunately, there is mounting evidence that John is not better than that.

And it is this evidence that calls into question whether McCain, his distinguished past service notwithstanding, retains the character – specifically the ability to react responsibly to pressure — that is required of a president.