The wild volatility in GameStop shares this year has emboldened Democrats who advocate a tax on stock trades.

A financial-transaction tax, or FTT, would raise money by collecting a fraction of the value of securities trades. Proponents say such a tax could help fund programmes such as President Biden’s $2tn infrastructure plan, while reining in high-frequency trading and excessive speculation. Critics, including Wall Street lobbying groups, say it is a flawed policy that would hurt investors.