Sen. Jon Kyl has done something very rare in Washington today. Compromise.

Last fall, the Arizona Republican was re-elected on a tough anti-immigration platform. But when Democrats took control of Congress his calculation shifted. “I had a choice,” he told The New York Times. “Do I sit on the sidelines and say, ‘that’s a bad bill?’ Or do I get in the fight and try to shape it as best I could?”

The bill Kyl helped write (with liberals like Ted Kennedy) has something for everyone to like -- and hate. Twelve million illegal aliens already here would get a shot at citizenship, but the process would be very long and arduous. And it wouldn’t even begin until many costly moves to reinforce the border were in place.

Still, Kyl’s role has stirred up a storm of scorn from conservatives back home. “He has betrayed the people who voted for him,” thundered state legislator Russell Pearce. “It’s absolutely a sellout of America.” And the senator has acknowledged the abuse: “I have learned some new words from some of my constituents.”

Well, we have our own word for Kyl. That word is “legislator.” And we mean it as a compliment.

Legislators see a pressing problem and try to solve it. They work with others, including folks from the other party. And they understand that “compromise” is not a dirty word. In fact, it is the very essence of the legislative process.

But it’s so easy to scream “sellout” and revel in purity and wash your hands of responsibility for actually getting something done. It’s so easy to say “I have my principles” and equate accommodation with betrayal. It’s so easy to play to the super-heated audience of interest groups, radio hosts and bloggers who enforce ideological conformity like an American Taliban. So easy and so wrong.

This is a very large and diverse country. Every one of the 535 members of Congress has his or her own principles. The only way government can work is for those lawmakers to reconcile principle with possibility, to understand that perfection should not be the enemy of progress.

President Bush, to his credit, has made reality the touchstone of his approach on immigration. “You can’t kick them out,” he said recently of the 12 million illegals: “That’s just not real.” And the president was right when he said the outcome of the debate hinges on this question: “Will members of Congress rise above politics?”