With the CNN debate between President Joe Biden and former President Donald Trump set to take place tonight, the former president and his allies are pre-emptively raging that the debate is unfair in case Biden outperforms the low expectations they’ve set with months of declaring him mentally infirm — and one of their biggest claims is that Biden is somehow being pumped full of drugs to improve his debate performance. But no such drug actually exists, pointed out former GOP consultant Stuart Stevens on X. “I am probably the only human on the planet who has taken a lot of performance-enhancing d…