Sometime in the next few weeks, Dem Rep. Sander Levin will introduce a bill that would require all presidential candidates to disclose 10 years of tax returns, as well as information about any offshore accounts, IRAs, or ongoing financial arrangements they benefit from, and any capital gains income they are earning.

Needless to say, this bill isn’t going anywhere in the House. It’s a conversation starter, and it points to another aspect of the debate over Mitt Romney’s tax returns that is getting lost: there’s actually a whole policy dimension to the argument over the returns that’s central to the presidential race.

Tax reform is central to the presidential campaign, and many of the questions surrounding it are all about how to approach the types of income Romney has earned — many details of which remain concealed in his unreleased returns.

“These issues all relate to tax reform — how we handle offshore accounts, how we handle capital gains, how we handle IRAs,” Rep. Levin told me this morning. “This is another reason Governor Romney should release his tax returns. As president, he would preside over tax reform.” Romney himself earns income from the very type of sources that would see a tax overhaul under reform, Levin added.

And so, Levin hopes that his bill — even if it is doomed — will force a debate over whether there should be a set of legal standards that govern the level of transparency required from presidential candidates. Such standards, of course, have been voluntarily followed by many recent candidates; Romney’s willingness to release only two years of returns makes him an exception. And so, Levin’s bill would amend the 1978 ethics in government law to spell out what candidates must make available to the public.

It’s likely that Dem Congressional leaders will support this bill, too. But of course, House Republicans all but certainly won’t. Indeed John Boehner and Paul Ryan are now defending Romney’s right to keep the returns shielded from public view, characterizing the push for release as a big distraction. Levin’s law won’t go anywhere. But perhaps it will force some needed debate — and will mean Republicans will be asked to comment on why they don’t favor a blanket set of standards for transparency from all presidential candidates.