The House of Representatives voted 252-175 Wednesday to establish an independent commission to investigate the Jan. 6 Capitol riot. It now heads to the Senate for approval, where resistance to the bill is mounting.

The decision comes after Senate Minority Leader Mitch McConnell announced his opposition to the legislation earlier Wednesday, signaling that the bill may garner insufficient Republican support to advance through the Senate. Among McConnell’s objections was the concern that the commission could interfere with existing federal prosecutions of rioters.

The legislation will require a 60-vote threshold in the split Senate to move forward.