Updated: 9:03 p.m.

Former Rep. Ernest Istook (R-Okla.) appeared on the House floor Tuesday evening to urge his former colleagues to vote against a debt limit plan offered by Speaker John Boehner (R-Ohio) — even as GOP leaders were aggressively pushing Members for support.

His presence in the chamber led some to question whether he violated House rules that prohibit former Members from lobbying on the floor.

Istook, a former appropriator who last served in Congress in 2007, is a distinguished fellow at the Heritage Foundation. He is not a registered lobbyist, but Howard Marlowe, president of the American League of Lobbyists, said that his registration status doesn’t matter and that “former Members are not supposed to lobby on the floor.”

But two other lobbying and ethics experts disagreed, saying the rules only apply to former Members who meet the definition of a lobbyist.

According to multiple sources who were present on the floor, Istook urged lawmakers to vote against the bill, which Heritage Action for America, a political organization associated with the foundation, is opposing.

His appearance on the floor is an indication of the high-stakes nature of the debt fight and Boehner’s struggle to secure enough votes to pass the bill.

A Heritage Foundation spokesman did not return a request for comment.