DETROIT — To know Mitt Romney is not to love him.

Just ask veteran Michigan Republican leader William Milliken.

There is no living political figure who has been more closely associated with the Romney family for more time.

Elected Michigan’s lieutenant governor as the running mate of Mitt’s dad, George Romney, in 1962. Milliken served at the elder Romney’s side from 1963 to 1969, during a period when they battled Barry Goldwater and the conservatives of their day for the soul of the Republican party.

When George Romney ran for the Republican presidential nomination as the moderate alternative to Richard Nixon in 1968 — mounting a campaign every bit as inept, if much more honorable in its goals and intents, than this year’s Romney debacle — Milliken was an ardent supporter of his ambitious friend and ideological comrade.

A year later, when George Romney left the Michigan statehouse to join Richard Nixon’s Cabinet, Milliken assumed the governorship. Like George Romney, Milliken attracted independent and even Democratic support to win election and reelection even in Democratic years, holding the state’s top job until 1983.

Still sharp, politically active and well-regarded in Michigan, Milliken might reasonably be expected to be on the Mitt Romney team this year. That was certainly Mitt Romney’s intent. The candidate courted Milliken, going so far as to meet with the former governor during a campaign swing through the state last year.

But Milliken is not campaigning for the son of his former running-mate going into Tuesday’s intense Republican primary in the Wolverine State.

Rather, Milliken has already cast an absentee ballot for Mitt Romney’s chief rival, Arizona Senator John McCain.

“I have long admired Senator McCain for his straight talk and service to the country,” says Milliken. “There’s a real sense of integrity in the firm positions he takes, even though they are not always popular. I don’t agree with him on all issues, but I like his well-earned reputation of saying what he means, and meaning what he says.”

Milliken is not exactly in the mainstream of the contemporary Republican party — he’s on the advisory council of Republicans for Environmental Protection, a group that has been at odds with the Bush-Cheney White House and most Republicans in Congress over issues such as global warming.

But he’s someone who knows the Romney family, someone who was a loyal political ally of George Romney and his wife, Lenore, for many years.

By most conventional political measures of personal and partisan loyalties, Bill Milliken should probably be with Mitt Romney this year. Certainly, the Romney campaign — which has stressed the father-son tie and other links between the former Massachusetts governor and Michigan — seems to think people who remember George Romney should back Mitt Romney.

Milliken does, indeed, remember George — fondly.

But he’s not backing Mitt.

That fact speaks volumes about the circumstance of what is looking more and more like it will be the second failed attempt by a Romney to win the Republican nomination for president.