Asked whether his former colleague Chuck Hagel could be a valuable Republican voice in an otherwise Democratic Cabinet, John McCain scoffed. To “allege that Hagel is somehow a Republican—that is a hard one to swallow.”

Of course, many have said exactly that same thing about McCain. That didn’t stop him from winning the Republican presidential nomination in 2008, en route to a lopsided loss to Barack Obama. Why should a self-appointed one-man credentials committee stop Hagel from becoming secretary of defense?

McCain’s Republican Party is defined by the foreign policy that drove George W. Bush’s presidency into a ditch, cost the GOP control of Congress, and committed the country to no-win wars—and isn’t done yet.

That’s why, unlike Hagel, Joe Lieberman is a member in good standing of McCain’s party. Lieberman also has “serious questions” about Hagel’s possible nomination. Unlike Hagel, he still caucuses with Senate Democrats, despite losing a Democratic primary in 2006. He voted for Harry Reid for majority leader.

Yet Lieberman won a prime speaking slot at the McCain-run 2008 Republican National Convention. He was active on the campaign trail. There’s no doubt McCain would support him for a Cabinet post. Indeed, there were reports that McCain even considered him for vice president in his own hypothetical administration.

As recently as 2000 Lieberman was the Democratic vice presidential nominee. He sought the party’s nomination for the top job, with the consistently liberal but intermittently hawkish New Republic’s blessing.

This would be like Hillary Clinton considering Dick Cheney in 2016, because he could bolster her left flank on gay marriage.

Lieberman’s lifetime American Conservative Union rating is 15.79. It was just 4 in 2010 and was zero as recently as 2005. Hagel’s lifetime rating was 83.7 upon leaving the Senate, higher than McCain’s the year he won the GOP presidential nomination.

As a senator, Hagel was pro-life, with 100 percent ratings from the National Right to Life Committee in 2005-06 and an 85 percent rating in his final year. Lieberman is pro-choice, voting even to keep partial-birth abortion legal, and has a zero from National Right to Life.

Lieberman voted against the tax cuts that congressional Republicans are at this writing fighting to preserve, at great political peril. (Come to think of it, so did McCain.) Hagel voted for them. Hagel sided with Republican presidential candidates, including Ronald Reagan, until McCain. Lieberman sided against them, including Reagan, until McCain.

Beginning to sense a pattern here?

Hagel has come under fire for opposing the nomination of James Hormel, an openly gay man Bill Clinton tapped for the ambassadorship to Luxembourg, and using some awkward language in doing so. But Hormel wasn’t just opposed by Hagel—he was opposed by social conservatives and many, if not most, Republicans in the Senate (Hormel was ultimately a recess appointment, so there was no official confirmation vote that would tell us for sure).

That might be a hanging offense in 2012. But 1998 was two years removed from when Democrats voted overwhelmingly (188 to 65 in the House, 32 to 14 in the Senate) for the Defense of Marriage Act and Clinton signed it into a law. Clinton himself had previously passed Hormel over for an ambassadorship to Fiji on the grounds that his activism and sexual orientation would be too provocative.

It’s one thing for gay rights activists and social liberals to be up in arms about Hagel’s history, though they might want to check the records of some Democrats in ’98. But for neoconservatives to bring it up is a bit rich. Did any of them oppose John Ashcroft for attorney general based on his stand against Hormel?

McCain embraces Lieberman while turning up his nose at Hagel because the former continued to champion the Iraq War long after his constituents had turned against it. By that time, Hagel had become a critic of the invasion and occupation. Also unlike Lieberman, Hagel has strongly indicated that he is not eager for a repeat in Iran or Syria.

The McCain-Lieberman tag team wants to paint Hagel as a radical for holding foreign-policy views far closer to those of most Americans than theirs. In fact, he is no radical. Hagel voted for the Iraq War and did not even turn as sharply against it as, say, Walter Jones. He is as innocuous an Eisenhower-style internationalist as one can find, albeit with the temerity to say publicly what many were saying privately about Iraq circa 2006.

The hysteria is designed to read people like Hagel, Jon Huntsman, and Jim Baker out of the foreign-policy mainstream as isolationists, bigots, and nutcases. Failing that, they can at least be read out of the Republican Party.

Will it work? In addition to failing McCain’s litmus tests for foreign policy, Hagel seems to share John Tower’s trait of having not got on famously with many of his colleagues. That was enough to doom Tower’s nomination for secretary of defense under George H.W. Bush.

But in terms of the larger project of making the GOP Joe Lieberman’s party, ask John Boehner how it works out when leaders whose conservatism is questionable to begin with start purging other Republicans.

W. James Antle III is editor of the Daily Caller News Foundation and a contributing editor to The American Conservative. Follow him on Twitter.