A large group of conservative activists and media figures -- including CNN's Erick Erickson and WND.com founder Joseph Farah - have published an open letter to House and Senate Republicans threatening them not to compromise in any way with the “leftist agenda” of the Obama White House and congressional Democrats, as reported by Ari Melber of The Nation. Aside from raising the specter of primary challenges for apostates, the signatories insist that the election actually showed that America is clamoring for conservatism.

According to the letter: “In the House, the nation elected in 2012 one of the largest Republican majorities in the past 100 years. You have a mandate to fight for conservative principles that is arguably much broader than the one that narrowly reelected President Barack Obama claims to have for his leftist agenda.”

“Arguably.” Indeed, one could argue that the reelection of the House Republican majority supersedes both the reelection of the Democratic president and the expansion of the Democratic Senate majority. There are just a few things you have to disregard: logical sense, the hard reality of the tax situation, and the available polling that shows public confidence in Democrats and the White House regarding the so-called “fiscal cliff.”

If you subscribe to the notion of an electoral “mandate,” to say that the House GOP came out of the election with a stronger hand doesn't wash. President Obama won reelection by a comfortable margin in the popular vote and with well over 300 electoral votes. The House Republican majority lost eight seats and the national popular vote, and likely owe the survival of their pared-down majority to the magic of gerrymandering.

Even if you were to dismiss the vote counts, there's still no getting around the fact that Republicans are in an untenable position with regard to taxes. The open letter is, in the end, all about taxes. Specifically, keeping taxes on wealthy people low. For all the words they waste on spending, many of the same conservatives who signed this letter either endorsed or said nothing about the spending increases under George W. Bush. What they are consistent on, however, is Grover Norquist-style anti-tax mania.

And when it comes to taxes, Congressional Republicans are in a bind. As Talking Points Memo's Josh Marshall writes, the question is not whether the top tax rate is going up (it is), but whether Republicans will make their already bad political situation worse:

Though there's still a lot of back and forth over it, Republicans realize that the top marginal tax rate is going up. This isn't even a matter of them 'caving' or the President 'winning'. Current law says they're going up. And there's no way to prevent that without a new law and the President's signature. So it's not just happening. For all intents and purposes it already has happened.

The only question is how quickly and under what circumstances everyone else's tax cuts will be extended. Indeed, made permanent. House Republicans can prevent those tax cuts by preventing such a bill from being voted in the House. But that's no more than the power to put a gun to your own head and threaten to shoot.

Looking a little more broadly, the conservative activists' claim that the House GOP has a mandate not to compromise doesn't mesh with the preponderance of post-election polling data that show the public backs the Democrats and the White House when it comes to pressing fiscal issues.

Americans overwhelmingly place more trust in Democrats and the president to avoid the “fiscal cliff” than they do Republicans, according to a Qunnipiac poll. If the Republicans dig in and we end up going over the “fiscal cliff,” the public will blame the GOP over President Obama by almost a two-to-one margin, according to a Washington Post poll. And this one's the cruncher: according to a Bloomberg poll, “President Barack Obama won the public argument over taxes so decisively that almost half of Republicans now say he has an election mandate to raise rates on the rich.” [emphasis added]

None of that adds up to a strong “mandate” for House Republicans. Indeed, the open letter from conservative activists is less a revelation of a mandate than a stark reminder of how politically perilous a situation the GOP finds itself in: hold fast and they'll be blamed for the consequences, compromise and they'll be savaged by their base.