JUKEBOX JOHN KEEPS CHANGING HIS TUNE…. The state Senate in Arizona approved an odious immigration measure yesterday, which, among other things, makes it a crime to lack proper immigration paperwork in the state, and “requires police officers, if they form a ‘reasonable suspicion’ that someone is an illegal immigrant, to determine the person’s immigration status.” Arizonans would be eligible for arrest if an officer thinks they might be an illegal immigrant and can’t prove otherwise.

The measure was strongly opposed by the state police chiefs’ association and immigrant-rights groups, but was embraced by Arizona Republicans. It was championed by a right-wing state lawmaker who used to be considered an embarrassment to the GOP, but has become increasingly influential as the party has shifted to the far-right.

It’s exactly the kind of effort Sen. John McCain (R-Ariz.) has long opposed. That is, previous versions of John McCain. The McCain now facing a right-wing primary challenger thinks this awful proposal is a fine idea.

Sen. John McCain praised a tough Arizona anti-immigration bill that will let police arrest people who aren’t carrying identification, the latest move in McCain’s rightward shift in advance of a tough Republican Senate primary this summer. […]

It’s a dramatic switch for a senator who supported comprehensive immigration reform with Democratic lion Sen. Ted Kennedy (D-Mass.) just four years ago. McCain is facing a primary challenge from the right in former Rep. J.D. Hayworth.

“He risked his political career for immigration reform, and now he is compromising his principles to fight for his political life,” said Frank Sharry, executive director of America’s Voice and a longtime immigration reform advocate.

Keep in mind, McCain wasn’t just a passive observer on this issue — he’s actually been a strong advocate of immigration reform, and has consistently been to his party’s left. He was, for example, a co-sponsor of the DREAM Act, which would grant legal status to illegal immigrants’ kids who graduate from high school. McCain also championed a 2007 effort on comprehensive reform, which included a path to citizenship that the far-right labeled “amnesty.”

And now look at him.

The politics of this are transparent. McCain is worried about losing to a right-wing primary challenger, so he’s abandoning his principles and previous positions. But the irony is, in his bid to look more appealing, McCain actually looks more ridiculous — the right knows his dramatic shifts on issues like immigration aren’t sincere, while those who’ve respected McCain’s willingness to break from the party line no longer recognize the political hack before them.

By trying to impress everyone, McCain is failing to persuade anyone.

Steve Benen

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.