HOPE VS. HATE…. Four years ago, the field of Democratic presidential hopefuls spent most of their time explaining how much different they would be from Bush/Cheney. Before long, Karl Rove sent out word to the Republican Machine: label the candidates and their supporters “angry.” The goal, of course, was to characterize Bush/Cheney as optimistic and hopeful, while painting Democrats as wild-eyed, rage-driven nuts.

It’s almost comical in retrospect.

Yesterday, John McCain delivered an unhinged anti-Obama diatribe in New Mexico, and when he posed a rhetorical question — “Who is the real Barack Obama?” — someone shouted, “A terrorist!” McCain paused momentarily, but did not comment on the remark.

Also yesterday, Sarah Palin repeated one of her unusually stupid attacks, rehashing the nonsense that Obama “pals around” with terrorists. One man in the audience, responding to Palin’s smear, shouted, “Kill him!” Palin also did not comment on the remark.

At the same Florida event, Republicans shouted abuse at journalists, hurling obscenities. The Washington Post reported, “One Palin supporter shouted a racial epithet at an African American sound man for a network and told him, ‘Sit down, boy.’”

And just to top things off, last night, the Republican Party of Pennsylvania announced its belief that Obama is “a terrorist’s best friend.”

I expected Republicans to fight hard to win this year. I also expected them to ignore traditional norms, throw caution to the wind, and dispense with honesty and decency. But I didn’t expect a wholesale descent into madness. These folks have just lost their collective minds.

Are McCain and Palin responsible for lunatics who shout insane comments at their rallies? Of course not. That said, when the Republican campaign, mired in desperation, deliberately stokes the fires of hate and fear, using disgusting lies to argue that Obama is literally dangerous, no one should be surprised when the far-right Republican base becomes frenzied.

The reckless and irresponsible rhetoric McCain and Palin have used has contributed to, if not practically created outright, an overheated political environment. It’s in this environment that furious right-wing activists feel compelled to use racial slurs against journalists, and shout assassination requests at political rallies.

The responsible thing for McCain and Palin to do would be to turn down the temperature a bit and insist, in no uncertain terms, that they have no tolerance for the kind of ugliness Americans saw yesterday from the GOP.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.