Stablecoin issuer Circle saw its stock drop by 20% following news that rival Tether, the largest stablecoin by market cap, had agreed to undergo a full audit by an unnamed "Big Four" accounting firm. This could pose a significant threat to Circle. The proposed Clarity Act market structure bill, which is still being revised by lawmakers, could also negatively impact Circle's share price. The company's shares have gained 170% since February, outperforming other crypto stocks and the struggling broader stock market.