The Senate voted last night to adopt a rule bringing more transparency to a practice long used to delay legislation. In a 92-4 vote, the Senate ended the “secret holds” that lawmakers used to anonymously hold up bills and nominees without having to explain their objections. The Senate’s new rule won’t prevent Senators from putting a hold on legislation—it’ll just make sure that senators who do so will have their name published in the Congressional Record.

As we noted a few weeks ago, secret holds allowed a single senator to sink the popular whistleblower protection bill at the end of the lame duck Congress. We still don’t know who that senator was, though the four senators who voted against ending secret holds yesterday could provide a clue.

Those four were South Carolina Republican Jim Demint, Utah Republican Mike Lee, Kentucky Republican Rand Paul, and Nevada Republican John Ensign.

Sens. Lee and Paul are freshmen members, so that rules them out. Sen. Demint and Sen. Ensign did not respond to repeated inquiries about whether they killed the whistleblower bill last year, according to a joint crowdsourcing effort by WNYC’s On the Media and the Government Accountability Project.

As Slate blogger Dave Weigel notes, Jim Demint, Mike Lee and Rand Paul are the three founding members of the senate’s Tea Party Caucus. Sen. Lee told Weigel that he opposed ending secret holds because he didn’t want to change the Senate’s rules.

A spokeswoman for Ensign told the Las Vegas Review-Journal that the lawmaker voted to preserve secret holds because he was dissatisfied with another portion of the bill on how long senators are allowed to review bills before voting.

As for Demint, this is at least his sixth time trying to block efforts to end secret holds. He told The Hill last year that there are “a lot of pressing issues that we face as a country,” but secret holds are not one of them.