William Milliken, a former Republican governor of Michigan, seemed to walk back his previous endorsement of McCain in an interview yesterday with The Grand Rapids Press.

“He is not the McCain I endorsed,” said Milliken, reached at his Traverse City home Thursday. “He keeps saying, ‘Who is Barack Obama?’

I would ask the question, ‘Who is John McCain?’ because his campaign has become rather disappointing to me.

“I’m disappointed in the tenor and the personal attacks on the part of the McCain campaign, when he ought to be talking about the issues.”

Milliken, a lifelong Republican, is among some past leaders from the party’s moderate wing voicing reservations and, in some cases, opposition to McCain’s candidacy.

Milliken stopped short of endorsing Obama, unlike Michigan Republican Phil Arthurhultz, a former state senator, who appeared with former Sen. Lincoln Chafee (R-R.I.) in Grand Rapids to support Obama.

Milliken illustrates the risk McCain is running by attacking Obama’s character. While it may stir up the base and increase conservative turnout — which worked for President George W. Bush and Karl Rove in 2004 — it seems unlikely to work this time.

Obama has broad appeal to independents and, apparently, moderate Republicans.

My colleague Sridhar Pappu wondered yesterday how this race would be shaping up if McCain had selected Sen. Joe Lieberman (I-Conn.) for his vice presidential nominee. He probably wouldn’t have to worry about swing-state moderates fleeing his own party.