You almost always hear it referenced as "Reagan's 11th Commandment." It is a simple, one sentence warning against intra-party divisiveness that dates back two generations:

"Thou shalt not speak ill of another Republican."

The irony, of course, is that while it is almost universally attributed to Reagan, he was not its creator. Indeed, the so-called 11th Commandment was not authored by Reagan, it was authored in order to protect Reagan.

The year was 1965. The Republicans had just been slaughtered in the 1964 electoral cycle, one of the most complete and total annihilations in the annals of American politics. Not only had Lyndon Johnson been re-elected with well over 60% of the vote, but Democrats had achieved nearly insurmountable two-thirds supermajorities in both the House and the Senate. When the 89th Congress was gavelled into session in early 1965, there were only 32 Republican Senators, and just 140 GOP members of the House.

Reagan was gearing up for a run for Governor of California. His primary rival was the former mayor of San Francisco, George Christopher. Christopher, given the fact that a former movie star would have a built-in reservoir of goodwill with voters, was going to need to go negative on Reagan in order to gain a foothold in the race.

He never got a fair chance to do so. Before Reagan had even formally declared for the race, California Republican Chairman Gaylord Parkinson made the decree that negative attacks in the primary would not be tolerated. Christopher went negative anyway, because, at the end of the day, he really had no choice. But now his attacks, once standard fare in political campaigns, had the official seal of disapproval from the state party. Reagan won the primary easily, and in a good Republican year in 1966, scored a double-digit win over incumbent Democrat Pat Brown in the general election.

While it is often invoked as some inviolate rule of Republican campaigning, the hard truth is that the "11th Commandment" has been oft-violated during the forty-four years since its inception. Including, as Brian Williams pointed out in a 2007 piece for MSNBC, by Reagan himself:

In 1976, Reagan was a former governor challenging an incumbent of his own party -- Gerald Ford -- for the Republican presidential nomination. Ford, who made no pretense of following the 11th Commandment (he said only that he would "abide by the first ten"), had beaten Reagan in the early primaries. Reagan’s campaign was faltering, and his own advisers urged him to take the gloves off. He did. Campaigning in Florida that March, Ronald Reagan broke the 11th Commandment and attacked Gerald Ford. He accused Ford, who had then been president just 19 months, of presiding over "the collapse of American will and the retreat of American power," and said Ford "must be held accountable to history for allowing this to happen." He said Ford lacked "vision," that he found it "difficult" to trust his leadership. He accused the president of favoring "pre-emptive concessions" in talks with the Soviet Union, and said, "I fear for my country when I see White House indifference to the decline in our military position."

That said, neither Parkinson nor Reagan probably could have envisioned today's GOP. In the past several months, the Republican Party has moved internecine warfare to a new level. The two most glaring examples were the sabotage of the party's own nominee in New York's 23rd Congressional District for insufficient conservatism, and the revelation this week that members of the Republican National Committee are pushing the idea of a proposed "purity test", a ten-point agenda (or, as Devilstower pointed out this morning, more of a promise to halt an agenda) that Republican candidates must adhere to in order to avoid being shunned by the GOP.

This is much bigger than a mere squabble among candidates in an open seat Congressional or gubernatorial primary. Both of these actions were, in their own ways, putting the official party imprimatur on purging unworthies from the party ranks.

So how do Republicans square these recent actions with staying true to the legacy of their patron saint?

Conservatives would no doubt argue that they are, in fact, preserving Reagan's Republican Party by making sure that it adheres to baseline principles that, in their view, are sacrosanct.

They want party unity, but they want it on their terms.

They are aided in this crusade by the fact that so-called moderate Republicans are so aware of their persona non grata status in the GOP that their desire to ingratiate the base knows no bounds.

In fact, two of the leading targets of the GOP purity crusade took the opportunity this week to remind Republicans that they really are, truly, one of them.

On Monday, Charlie Crist, who is increasingly imperiled in his desire to move from Governor of Florida to Senator from Florida, wanted to make it clear that he was every bit as committed to the right-wing values of the teabagger base as his insurgent opponent:

"It's hard to be more conservative than I am on issues -- though there are different ways stylistically to communicate that. I'm pro-life, I'm pro-gun, I'm pro-family and I''m anti tax," the governor explained.

Meanwhile, the woman who was drummed out of the special election in upstate New York, DeDe Scozzafava, also wants people to know that in spite of her purging during the course of the battle in NY-23, her Republican bonafides are still largely intact:

Dede Scozzafava, the Republican candidate in NY-23 who eventually dropped out after incurring the wrath of conservative acvists, says she would have fared pretty well on the so-called GOP "purity test." "I would have been at seven out of 10 on the list," Scozzafava told CBS's Face the Nation.

Leaving aside for the moment that 70% would be scored as an "F" on the GOP purity test as it is currently configured, it is telling that Scozzafava still feels compelled to remind voters just how much of a Republican she really is, despite the high-profile way in which the national party turned its back on her and embraced her third-party opponent, Doug Hoffman.

This is the reason why purity test author Jim Bopp (an RNC member from Indiana) made clear that past votes matter little in the calculation of ideological purity. What matters more, in his calculation, is what is done and said from this point forward.

The purity movement, in that respect, is less about igniting a civil war in the Republican Party as it is about trying to reposition the Republican Party further to the right. In this way, it is trying to be true to Reagan (though one with a sense of history might wonder how St. Ron would fare himself on such a purity test) while ignoring the 11th Commandment often attributed to him.

To do so successfully, they will need the so-called centrists to capitulate to the right. That might be a safe bet. In October, we had Connecticut Senate candidate Rob Simmons, in an act that bordered almost on parody, proclaiming that he would be adding a teabag to his copy of the Constitution. Earlier this month, Mark Kirk alienated longtime supporters in the abortion rights movement by voting in favor of the Stupak-Pitts amendment.

In an election year where a vast enthusiasm gap could create a perilous political environment for Democrats, these recent developments could be the saving grace for Democrats.

Indeed, it could be the salvation of the Democratic majority, no matter how it turns out. If so-called moderate Republicans resist this rebranding of the GOP, then the dissension will clearly do harm to GOP designs on shrinking the Democratic majority. We saw this in the New York 23rd, where a district with a sizeable GOP registration advantage turned to Democrat Bill Owens after the more moderate of the two Republicans running (Scozzafava) was driven from the race.

However, even if the purity movement succeeds, and the "moderate" Republicans are assimilated, that could benefit the Democrats, as well.

When the traditional media absurdly tut-tutted the challenge to Joe Lieberman in 2006 as a sign of Democratic intolerance of diverse views, they missed a key point. At the exact same time Lieberman was getting primaried by Ned Lamont, the most conservative member of the Democratic Senate delegation was being ignored. Ben Nelson of Nebraska did not face a primary challenge, either high-profile or low-profile.

The bottom line was simple: Nelson's apostasy was less obscene than Lieberman's, if for no other reason than simple political geography. Nebraska ain't Connecticut, to put it mildly.

Republicans, in their fervor to rebrand the party, might be ignoring that lesson to their detriment. Insisting on rigid adherence to party orthodoxy might not hurt them in some states, but it is hard to see where a Mark Kirk, a Rob Simmons, or a Mike Castle gets traction running as an advocate of teabagger Republicanism.

We have already seen some evidence of this. In Delaware, the most recent poll from Susquehanna Research (a firm that also does private work for GOP candidates) found that Beau Biden now leads Republican Mike Castle in the state. This represented an incredible shift in voter preferences: a twenty-six point shift in eight months, according to the same pollster. No other pollster this year had given Biden the lead.

Therefore, there is a certain impracticality to this GOP purity crusade. Conservative ideological policy sell well in certain arenas, but less so in others. The problem for the GOP is that several of their most high-profile targets are in blue or purple territory.

That said, Democrats cannot merely rely on being saved by the possibly errant tactics of their opposition. They could control their own electoral destiny by putting together a series of accomplishments to take to the voters in 2010. The clock is ticking.

Absent that, the best the Democrats could hope for is that the GOP's purge of its unworthies and insistence on ideological unanimity might save a few Congressional seats that otherwise would have been imperiled.