Hillary Clinton's decision to push for a gas tax holiday, especially in the face of unanimous expert opposition, failed as a tactical move. Obama performed better than expected from the final polls before Tuesday's primaries, and the gas tax was a major reason why.

Clinton's strongest positive argument for her candidacy is her policy experience, the idea that she would be "ready to lead day 1". She had the reputation of being a top-notch policy wonk, mastering the nitty-gritty details of complex policy issues. But her handling of the gas tax holiday undermined that image.

First, the suggestion itself was widely opposed as a short-term gimmick. But because she thought it was helping, she continued to push it in the face of universal expert opposition. When neither she nor her surrogates could name a single economist who supported the plan, her campaign instead started attacking the credibility of economists. That was a fatal mistake - not because the general public has any particular affinity or love for practitioners of the dismal science - but because it undermined her image of truly being an expert policy wonk. It's hard to out-wonk economists, and by dismissing them outright because they opposed the gas tax holiday, Clinton made herself look foolish and inexperienced.

And if she's not a policy expert, then the positive case for her candidacy is greatly weakened. More voters started to see her advocacy of the issue as craven pandering, not a genuine proposal seeking to help the working class. So the issue, rather than bolstering her as a friend of the working class, reinforced her image as an opportunist willing to say or do anything to get elected, while undermining her aura of policy expertise.

She went for a "Hail Mary" pass by first pushing the gas tax holiday, then doubling down her advocacy in the face of unanimous expert opposition. And instead of giving her a big break, it weakened her further.