I like John McCain. I have liked him for a long time—even when he got angry with me one night years ago in the green room at CNN. (In fact, on that occasion, he taught me an important lesson about civil disagreement—that it is OK to challenge someone’s judgment or disagree with his or her positions, but not all right to impugn motives or attack someone personally. While I didn’t think at the time that I had done that, I became a lot more careful in the future. And I commend that advice to the extreme voices that use hateful words and demonize opponents on talk radio and during many of the TV cable shows on both the right and the left.)

I have also liked Sen. McCain’s (R-Ariz.) willingness to reach across the aisle over the years and work with Democrats on bipartisan legislation. This is what he did in sponsoring campaign finance reform with liberal Democratic Sen. Russ Feingold (Wis.), showing no small degree of political courage in standing up to his conservative base, which opposed such reform.

Even where I have thoroughly disagreed with him on issues—such as his 100 percent support for intervention by way of a pre-emptive attack on Iraq or his opposition to President Barack Obama’s national healthcare bill—I have respected his sincerity and authentic conservative principles.

I recall being inspired by McCain’s willingness to be open-minded on the issue of climate change. And while many of us anti-Iraq war Democrats were 100 percent convinced that the “surge” in Iraq that McCain supported would be unsuccessful (including, at one point, President Obama), events proved we were wrong and Sen. McCain was right.

Most of all, I admired McCain’s willingness (along with that of his equally politically courageous friend, Republican South Carolina Sen. Lindsey Graham) to take the lead on comprehensive immigration reform. It was McCain who joined with Democrats—and with then-President George W. Bush—to support a comprehensive immigration reform bill, one that would create a pathway to citizenship for the estimated 11-12 million-plus undocumented “illegal” aliens while enhancing and providing extra funds for border security.

He exposed himself to attacks from the right of his Republican Party base, which accused him of favoring “amnesty” for illegal aliens—a charge by definition false, since “amnesty” is defined as complete forgiveness, whereas McCain’s and Bush’s proposal (supported by many Democrats) would require illegal aliens to pay fines and meet other requirements before, over time, being granted citizenship.

During his run for the 2008 Republican presidential nomination, McCain downplayed the “pathway to citizenship” aspects of his position and emphasized his border-security stance—and I understood that. Politics is politics—and McCain deserves more of a cushion, in my mind, given his record of authenticity, courage and bipartisanship.

But then came the last several days. The state of Arizona passed an abominable, literally indefensible and obviously unconstitutional law that would allow police officers to stop anyone they “reasonably suspect” of being undocumented. Anyone who can add two and two would have to concede that this will lead to—no, will require—racial profiling by police officers. How else will a police officer “reasonably suspect” someone of being undocumented unless his or her were dark or he/she spoke with an Hispanic accent? To ask the question is to answer the question.

Worse, the bill would require the arrest of anyone who couldn’t produce “papers” proving their documented status. Is there anyone who doesn’t think of Nazi Germany or the movie “Casablanca,” when the German SS walked through Rick’s Casino demanding that all show their “papers”? One shudders at the memory of this type of fascist-state culture—until you realize that is exactly what the Legislature of Arizona and Republican Gov. Jan Brewer just signed into law.

And what did McCain say? He supported the law because people are “frustrated” at the absence of border security. He is also running in a primary against conservative talk show host and former Rep. J.D. Hayworth, who praised Brewer and the law.

Even Florida Tea Party Senate candidate Marco Rubio opposed the bill as “government overreaching”—and former Florida Gov. Jeb Bush warned that the bill would lead to racial discrimination. Sen. Graham, while decrying the lack of border security and pointing up the genuine fear of citizens who live along the borders, still called the Arizona bill unconstitutional.

So is a Senate seat really worth it, Sen. McCain, to go against everything you have stood for through the years as a voice of integrity and courage in the U.S. Senate? Can you really look into the mirror and say the words, “Show me your papers”?

Your fans, including many Democrats like me, want to believe it really ain’t so that you support this bill, even if you won’t say it ain’t so.

This piece appears today, April 29, 2010, in Mr. Davis’s regular weekly column in The Hill “Purple Nation.”

Davis, a Washington lawyer and former special counsel to President Clinton from 1996-98, served as a member of President George W. Bush’s Privacy and Civil Liberties Oversight Board in 2006-07. He is the author of Scandal: How ‘Gotcha’ Politics is Destroying America (Palgrave Macmillan, 2006).