Editor's note: John P. Avlon is senior political columnist for The Daily Beast and author of the new book "Wingnuts: How the Lunatic Fringe is Hijacking America."
(CNN) -- She was caught red-handed. The surreal scene of Sarah Palin referring to notes written on her palm during a Q&A session after her speech at the National Tea Party convention has validated skeptics even as it's been dismissed by her supporters.
This disconnect is a real problem for Palin and the Republican Party. Palin's presidential hopes are already confronting the fact that she is the most polarizing figure in American politics.
She is queen of the conservative populists, and to her supporters she can do no wrong. She is despised by Democrats. But -- and here's the biggest hurdle -- she is disliked and distrusted by Independents and centrists.
Palin's "Palm-gate" incident matters because it validates the doubts deeply held by Sarah skeptics in the center of the American electorate.
I was in the room when she gave her speech at Nashville's Opryland Hotel. It was well-written and rapturously received by the Tea Party crowd. It was part campaign speech and part state of the union address, focusing on foreign policy for the first 15 minutes -- a subject rarely discussed inside the Tea Party movement -- before she got to the red meat of deficits and debt.
It had a string of her patented folksy and sarcastic one-liners, such as "How's that hopey-changey thing working for ya?" It brought the house down. And then there was the one-liner that would haunt her a few minutes later: a dig at President Obama as "a charismatic guy with a teleprompter."
Ironically, Palin is a charismatic gal who could have used a teleprompter that night. It would have helped her avoid looking down at her text half the time, and it would have slowed her delivery to the pace she used in her devastatingly effective 2008 convention address.
But she presumably avoided a teleprompter in part to use that one line -- and the audience loved it. When it came time for the post-speech question-and-answer session, no one announced that she had been given the questions in advance. It wouldn't have sounded very populist.
But that's the only explanation for why she had written notes on her hand. That such a stunt would get a kid kicked out of a junior high classroom isn't the point -- the real problem is the question that prompted the note-taking.
Palin was asked to recommend the top three things Republicans should do when they retake Congress. The follow-up was the first three things she would do if elected president.
She wrote on her hand the following notes: "energy"; "budget cuts" ("budget" was then crossed out and replaced with "tax" -- presumably because a call for budget cuts would require sticky specifics); and "lift American spirits" -- the last being a call for more reliance on God in our politics.
The questions would have been softballs even if she hadn't seen them in advance. The answers are so boilerplate that a candidate for city council wouldn't need prompting.
That Palin believed she needed to write them down is the political equivalent of reminding yourself to breathe. The gap between Palin's scripted surgical strikes in her speech and the need to rely on notes for a simple question she saw in advance validates the doubts that nonconservatives have long had about her.
A poll taken toward the end of the 2008 campaign found that 47 percent of centrists said her selection made them less likely to vote for John McCain as president. A July 2009 Washington Post/ABC News poll showed that 58 percent of independent voters did not believe that she understood complex issues.
Palin's Palm-gate only compounds these problems. No one should doubt Palin's appeal to the conservative base -- she is beloved beyond reason, seen as the embodiment of God and Country, the "real America" antidote to the multicultural elitism some Tea Partiers associate with Obama.
Any mistakes she makes between now and the nomination will be dismissed by her supporters as the liberal media playing "gotcha" politics. No other prospective GOP candidate for 2012 can match her fans' enthusiasm, and she will be the biggest draw on the 2010 midterm election circuit.
That's enough to win the pivotal first Iowa caucus and possibly the 2012 nomination. But in an America where independents outnumber Republicans or Democrats, fielding a presidential candidate with negative crossover appeal is a path to electoral disaster.
The opinions expressed in this commentary are solely those of John Avlon.