MITT ROMNEY is zero for two when it comes to transparency in campaigning.

First, Mr. Romney — breaking with the practice of previous Republican presidential candidates, including George W. Bush and John McCain — has refused to release the identities of his bundlers, the well-connected fundraisers who help the campaign haul in stacks of checks adding up to hundreds of thousands of dollars. Mr. Romney is under no legal obligation to reveal his bundlers, other than the relative handful who are also registered lobbyists.

But that is not, or at least should not be, the end of the discussion. As Mr. Bush and Mr. McCain, among others, recognized in agreeing to reveal the identities and, within broad categories, amounts collected by their bundlers, the flood of details about relatively trivial campaign donations is far less important than knowing the identity of these essential supporters. Federal election law requires that campaigns report the names of those giving $200 or more, but the existence and proliferation of bundlers means the truly valuable information, about which fundraisers the campaign is most indebted to, remains secret. Mr. Romney’s position is an unfortunate step back.

Now Mr. Romney has doubled down on this lack of transparency, telling NBC that he does not intend to release his tax returns even if he becomes the Republican presidential nominee. “Never say never, but I don’t intend to do so,” Mr. Romney said Wednesday. On Thursday, that stance seemed to be softening somewhat, to: “We don’t have any current plans to release tax returns, but never say never.’’ This is unacceptable and, as with the Romney campaign’s stance on bundlers, a sharp departure from previous practice. Some presidential candidates, including Hillary Rodham Clinton (D) and John McCain, balked — incorrectly in our view — at releasing tax returns during the primary season.

Yet it has become a given that nominees, much like presidents and vice presidents, release their income tax returns. Texas Gov. Rick Perry (R) has released his, and former House speaker Newt Gingrich (R) pledged he would do so upon becoming the nominee. As with bundlers, Mr. Romney hides behind legal requirements. It is true that candidates are required to file financial disclosure forms, but tax returns provide information not otherwise available, including charitable contributions and effective tax rates.

During Mr. Romney’s 1994 bid to unseat Sen. Edward M. Kennedy (D-Mass.), he called on the senator to release his tax returns to prove he had “nothing to hide.” Yet Mr. Romney did not release his own returns during that campaign or his subsequent run for, and service as, governor. Would a President Romney release his tax returns? We posed that question to his campaign, twice, and did not receive an answer.