I thought we already knew this, but CSM’s story about it yesterday got a lot of play, so maybe we only thought we knew it. Or maybe we knew she was speaking but not necessarily keynoting.

Now it can be told: She is.

On its face, the gig would seem a step down for Ms. Palin, one of conservative America’s most popular and polarizing figures (not to mention major thorn in the side of the Obama White House).

But with an NBC/Wall Street Journal poll ranking a generic “Tea Party” as more popular than either Democrats or Republicans, and Palin herself rivaling the charming Mr. Obama in poll popularity, many experts see the Tea Party event as a potential milestone for a mounting, even transformational, force in US politics…

But courting what many call a fringe and inchoate movement carries huge risks, argues Alan Abramowitz, a political scientist at Emory University, in Atlanta.

He says a Republican shift toward the Reaganesque Tea Party ideal could lead to a sort of pogrom for moderate Republicans, forcing out those (think Maine Sen. Olympia Snowe) who don’t hew precisely to rock-hard conservative principles around economic freedom and limited government interference…

Solidly behind that assessment, Democrats are aiming to vilify the rising Tea Party movement as woefully old-school and out of touch.

Here’s the convention homepage; if you’re planning on going, I … assume you’re wealthier than I am. Choosing Sarahcuda for the keynote is in some sense an easy call — she’s the undisputed rock star of rock stars among grassroots conservatives — but it’s odd to me that a movement devoted to taking back Washington would hand its biggest spotlight to someone who’s not running for office in 2010. Isn’t there a certain would-be “tea-party senator” who’d benefit from this free publicity more than a woman who’s done O’Reilly, Limbaugh, and, oh yeah, Oprah just within the last three months? If they’re serious about electing “true conservatives” to restore small government principles next year, there’s no time like the present to start boosting actual candidates.

In fairness, Palin’s speech will be more interesting than whatever Rubio would say just because she’ll be under pressure to extol the independent, nonpartisan nature of the tea parties — after having agreed with Rush two months ago that no, of course America’s not ready for a third party. No biggie if she does, though: She’s leveraged her tea-party appearance with another speaking engagement at the Southern Republican Leadership Conference. Exit question: So, who’s going to Nashville?