The Senate Campaign Disclosure Parity Act is a bill that you wouldn't think anyone could possibly be against. And yet, the Republican leadership in the Senate has gone to considerable lengths to stop it -- recently by brazenly insisting on an amendment that would effectively discourage groups from filing ethics complaints against senators. Without that amendment, which Democrats reasonably call a poison pill designed to sink the bill, Republicans say it's not going anywhere.

Here's what the bill would do. Candidates for the Senate file paper versions of their campaign disclosure reports. The bill would require those reports to be filed electronically. That's it.

The House moved to that system six years ago -- which is why it's called the campaign disclosure "parity" act. The bill has forty co-sponsors, among them conservative Republicans, such as Sens. Thad Cochran (R-MS) and John Cornyn (R-TX). A cynic might say that the only rational reason for opposing the bill would be if you wanted to make it harder for people to discover who's been giving to your campaign.

When the bill came to the floor this spring, it was blocked twice by an anonymous Republican senator, using what's called a "secret hold." (Here's our hunt last summer for those behind secret holders on another bill.) But that tactic was forbidden by the Democrats' recent ethics bill, and so when the bill came up again earlier this week, the senator who came forward to block it identified himself. It was Sen. John Ensign (R-NV).

Only Ensign didn't say that he was blocking it. In fact he said that he has "no objection" to the bill. But he insisted on offering an amendment. His bill would require all non-profits that file ethics complaints against senators to disclose all donors who gave $5,000 or more. His bill, he said on the floor, was designed to "protect individual Senators from purely politically motivated ethics complaints that come against us that sometimes we will have to run up legal bills and all kinds of other things." Without any evident irony he added: "transparency is the best way to do it."

The political nature of Ensign's strategy is, well, transparent. When I contacted Sen. Ensign's office for an explanation, for example, I was referred to Ensign's spokeswoman at the National Republican Senatorial Committee, of which Ensign is chairman. Rebecca Fisher explained via email that Ensign "doesn't oppose the bill" and only opposed Democrats seeking to pass it by unanimous consent (a much quicker method used for bills without opposition). And to my question of whether Ensign was the one behind the previous "secret holds," she answered straightforwardly, "Sen. Ensign did not have a secret hold, or any hold, on the bill."

That may be true, since Ensign is certainly not alone. As Roll Call reported yesterday, Ensign freely admitted that he'd discussed the issue with other members of the Republican leadership before insisting on his amendment. And the Sunlight Foundation, which has been bird-dogging the issue for months, long ago identified Senate Minority Leader Mitch McConnell (R-KY) -- that great foe of campaign finance reform -- as the main culprit.

For now, McConnell insists that he's not blocking the bill. “If [the Democrats] give us an amendment, we’d be done in a half an hour," McConnell's spokesman told Roll Call.

Watchdogs, at least, think the issue is clear. Ensign's (or McConnell's, if you prefer) amendment is obviously targeted at Citizens for Responsibility and Ethics in Washington, which has filed a number of ethics complaints of late against Republican senators, such as Sens. David Vitter (R-LA), Ted Stevens (R-AK), and Larry Craig (R-WY). "I think Sen. Ensign should look at the ethics issues of members of his caucus like Vitter and Stevens and spend less time worrying about how CREW is funded," the group's spokeswoman Naomi Seligman Steiner told me. "But we're glad we're on his radar. Clearly he's concerned about us. Maybe we're making a difference. That seems OK to me."

Chris Farrell of Judicial Watch (which has filed complaints against Sen. Harry Reid (D-NV) and others) had a similar take. "That sounds to me like an attempt to suppress scrutiny.... It's a sad reversal of the kind of scrutiny there ought to be of politicians who use their office to broker favorable deals for themselves."