I’ll admit it was difficult to watch former Sen. Chuck Hagel being grilled – or perhaps I should say “charbroiled” – by his former colleagues on the Senate Armed Services Committee.

Hagel is President Obama’s pick to be defense secretary and he came under intense fire – some news outlets referred to it as “friendly fire” – over comments he has made in the past about Israel, Iran and gay people.

Particularly troubling was the bitter fusillade launched at him by Sen. John McCain, R-Ariz., over statements Hagel made about the troop surge in Afghanistan. McCain insisted that Hagel give him a “yes or no” answer as to whether he still supported his stated view that Obama’s troop surge was a gross error. Hagel wouldn’t answer it the way McCain wanted. Instead, he preferred to explain himself in detail. McCain would have none of it.

The exchange was tense and it had an odd taste of bitterness coming from McCain.

The oddity of it stems from McCain and Hagel’s relationship. They’re both Republicans. They both are decorated veterans of the Vietnam War. They had been close allies while serving together in the U.S. Senate. What’s more, Hagel was McCain’s campaign manager when McCain ran for president the first time in 2000. I’ve noticed several pictures of the two of them during that campaign, with Hagel standing by his man as McCain was being pilloried in a ghastly attack launched by then-Texas Gov. George W. Bush’s campaign during the 2000 South Carolina GOP primary.

Hagel and McCain were thick back then.

Now, though, as Hagel seeks to become defense secretary in the Obama administration, we’ve heard McCain take a decidedly different tone when speaking to and about his former colleague and (presumably former) friend.

How can that be?

Well, it might have something to do with the individual who has tapped Hagel to lead the Pentagon. Barack Obama gave McCain a thorough drubbing in the 2008 election. I’m wondering now if McCain and other Republicans aren’t ticked off a bit more than usual because one of their own has agreed to work with a Democratic president who twice has kicked their backsides.