Ronald Reagan often spoke of the 11th Commandment: “Thou shalt never speak ill of another Republican.” Of course, as a competitor in the 1976 GOP primary Ronald Reagan certainly spoke ill of Gerald Ford and Rockefeller Republicanism in general.

But he never compared a Democrat favorably to Ford or any other Republican.

He understood that however vigorous internal party competition should be, no Republican should ever openly praise a Democrat at the expense of his own party. One could work across the aisle whenever possible and one could praise certain members of the other party, but one should never rally in defense of the standard bearer of the other party to critique one’s own. That would be the essence of party disloyalty.

Well, Democrats largely believe in the same principle. It’s one thing to cross the aisle and work with Republicans on legislation. But it’s another to embrace the Republican Party’s standard-bearer and positions as a cudgel against the Democrats. We call this Zell Millerism, or more recently, Joe Liebermanism.

Say what you want about the politics and character of Zell Miller and Joe Lieberman, but core Democrats would never support one of them for the Presidency anymore. Party loyalty still matters.

Hillary Clinton today pushed an increasingly obnoxious line against Barack Obama about his supposed lack of credentials to serve as Commander in Chief. No fewer than three times now, she’s said that both she and John McCain have the experience necessary to be Commander in Chief but all Obama has is a speech in 2002. This line is disingenuous - Obama passed a signature nuclear non-proliferation law with Richard Lugar, for example - and Hillary Clinton hasn’t exactly reeled off the most impressive array of national security accomplishments in her own right. But by bringing McCain into it, she risked bolstering the Republican candidate who she hoped to defeat herself. It seemed dangerous.

But today she crossed over a “threshold” with a major gaffe that she will need to address very quickly.

“I think that since we now know Sen. McCain will be the nominee for the Republican Party, national security will be front and center in this election. We all know that. And I think it’s imperative that each of us be able to demonstrate we can cross the commander-in-chief threshold,” the New York senator told reporters crowded into an infant’s bedroom-sized hotel conference room in Washington.

“I believe that I’ve done that. Certainly, Sen. McCain has done that and you’ll have to ask Sen. Obama with respect to his candidacy,” she said.

Calling McCain, the presumptive GOP nominee a good friend and a “distinguished man with a great history of service to our country,” Clinton said, “Both of us will be on that stage having crossed that threshold.”

Not only does she now think that she and McCain have the experience to serve as Commander in Chief, but that she and McCain have both crossed some sort of threshold where they are acceptable as Commander in Chief - and that Obama presumably has not. This is beyond dangerous and is now self-destructive on several levels.

1. She just gave McCain ammunition in a fall general election matchup between Obama and McCain. All McCain has to do is run an ad saying, “Even Hillary Clinton believes I’m more qualified to be Commander in Chief than Barack Obama…”

2. She violated the 11th Commandment by undermining party values in inferring that McCain is actually a more qualified Commander in Chief than Barack Obama. Most Democrats vehemently disagree with the notion that McCain is better on this. They understand that Commander in Chief means having the judgment, temperament, strategic acumen, management expertise and courage to run the military. And since John McCain has openly called for a 100-year occupation of Iraq and a war with Iran - positions that most Democrats find despicable - there is no reason ANY Democrat should be conceding John McCain’s fitness for Commander in Chief. His personal military background is impressive and heroic, but it is far from sufficient in preparing someone for Commander in Chief.

3. She neutered herself in a general election matchup, even if she were the nominee. By conceding John McCain’s acumen as Commander in Chief, she has no ability to attack him on those grounds. It’s one thing to recognize his experience. It’s another to say he’s crossed the threshold into acceptance. Imagine, for a moment, if John McCain conceded the economy or health care to Hillary Clinton. It doesn’t matter that the nation as a whole would agree that she’d be better on those issues than McCain. It’s just political suicide to concede those things in a primary race when you’re going to need to fight those positions in the general election.

A day after some good press for surviving in Texas and Ohio, Hillary Clinton seems to have let her national security strategy get to her head. Democratic voters will not be impressed by her insinuation that McCain would be a better Commander in Chief than Barack Obama. It’s one of the gravest acts of party disloyalty you can commit in a primary.

And what’s strange is that it’s completely unnecessary.

She can make a claim about being a better leader on national security without praising McCain in the process. It seems like she imagines Pennsylvania Democrats to be a bunch of Deer Hunter Reagan Democrats who love the Iraq war. Strangely enough, some of the staunchest anti-war Democrats in Pennsylvania are John Murtha, newly elected Joe Sestak, newly elected Patrick Murphy (Iraq war veteran), and conservative Rep. Chris Carney. Pennsylvania Democrats hate the Iraq war, and they don’t want their party’s standard-bearer conceding that hardcore neoconservative John McCain is the better Commander in Chief.

This gaffe - coupled with revelations that the whole NAFTA flap may have been initiated by Clinton’s campaign and not Obama’s - will seriously undermine any positive press she got after March 4.

But for loyal Democrats who do not, in fact, trust recently-blessed-by-George-W.-Bush John McCain as Commander in Chief, Hillary Clinton has a lot to explain.

Cartoon by Adam Zyglis, The Buffalo News

More reaction from blogs HERE.