Which amendment prevents Congress from increasing its members' salaries right before elections?

The Twenty-Seventh Amendment to the United States Constitution plays a crucial role in regulating congressional pay. This amendment states that any change in the compensation for members of Congress cannot take effect until after the next election of representatives. This provision serves as a check on congressional power, ensuring that lawmakers cannot vote to give themselves a pay raise or reduce their salary in proximity to an election. It promotes accountability and transparency, directing that the potential consequences of such salary changes will only be felt by those who are elected after the change is enacted. This prevents any immediate impact on their earnings from decisions made during their current term, incentivizing them to consider the opinions of their constituents before implementing pay changes.

In contrast, the other amendments mentioned do not relate to congressional salary adjustments. The Twenty-Third Amendment addresses the electoral votes for the District of Columbia, the Twenty-Fifth Amendment clarifies presidential succession and disability, and the Twenty-Sixth Amendment lowers the voting age to eighteen years, none of which pertains to the regulation of congressional pay.