A Twitter buddy reminds me that this is technically old news. The LA Times published a long, detailed piece about it in 2007. But then, Romney’s support for the mandate is also technically old news and yet Republicans care about it a lot more this time than they did last time. As the national debate changes, so do the issues that matter to voters. Go figure.

Does this matter?

In addition to paying the lower tax rate on his [domestic] investment income, Romney has as much as $8 million invested in at least 12 funds listed on a Cayman Islands registry. Another investment, which Romney reports as being worth between $5 million and $25 million, shows up on securities records as having been domiciled in the Caymans…

Romney campaign officials and those at Bain Capital tell ABC News that the purpose of setting up those accounts in the Cayman Islands is to help attract money from foreign investors, and that the accounts provide no tax advantage to American investors like Romney. Romney, the campaign said, has paid all U.S. taxes on income derived from those investments.

“The tax consequences to the Romneys are the very same whether the fund is domiciled here or another country,” a campaign official said in response to questions. “Gov. and Mrs. Romney have money invested in funds that the trustee has determined to be attractive investment opportunities, and those funds are domiciled wherever the fund sponsors happen to organize the funds.”…

Tax experts agree that Romney remains subject to American taxes. But they say the offshore accounts have provided him — and Bain — with other potential financial benefits, such as higher management fees and greater foreign interest, all at the expense of the U.S. Treasury. Rebecca J. Wilkins, a tax policy expert with Citizens for Tax Justice, said the federal government loses an estimated $100 billion a year because of tax havens.

Supposedly, Bain Capital maintains no fewer than 138 “secretive offshore funds” in the Caymans. To reiterate: No one’s claiming that Romney is using a tax shelter for his own money here. He’s paying the normal rate. (ABC’s headline is highly misleading on that point.) The claim, rather, is that the funds created by him and Bain operate as a tax shelter for other investors — specifically, per the LA Times piece, nonprofit institutional investors like pension plans and university endowments, which can avoid the 35 percent federal tax on “unrelated business income” by investing in an offshore hedge fund instead of a domestic one. Those investors get a little extra cash from that tax break plus higher foreign interest, Bain and Romney get some extra cash from higher management fees plus the profits that came from attracting additional investors, and everyone’s happy — except the IRS.

Which brings us back to the key question: Does this matter? Not as much as it would if Romney was sheltering his own dough, certainly, but it’s easy to imagine The One on the stump this fall talking about Mitt and his old company (whose profits he still shares in) making bank by helping others avoid the taxman while Joe Sixpack has no recourse but to pay up. If you think that’s a big nothingburger and are willing to go to war to defend perfectly legal tax shelters, okay, but this is yet another reason why we’d better see Romney’s tax returns now, not later. I appreciate Mitt not wanting to provide Democrats fodder for class-war demagoguery, but if we’re going to invest in Romney Inc in hopes of a big dividend in November, let’s see a prospectus so that we know exactly what liabilities we’re taking on. Read NRO’s new editorial for more on that.

Update: After re-reading the LA Times piece, it looks like I conflated two different funds above. It’s a shell company in Bermuda, not the Caymans, that helps institutional investors avoid certain taxes. The Caymans shell company is aimed at “shield[ing] foreign investors from U.S. taxes they would pay for investing in U.S. companies.” Same left-wing political attack applies — Bain and Romney are helping their wealthy clientele to avoid paying their “fair share” in taxes — but the specifics are apparently a bit different.

Update: ABC’s now changed the headline. It used to read “Romney Parks Millions in Offshore Tax Haven.” Minor problem: It’s not actually a tax haven for him. He pays the same tax on that money as he does on his U.S. investments. Now the headline reads “Romney Parks Millions in Cayman Islands.”

Update: By the way, even Romney fan Chris Christie thinks Romney should release his tax returns.