Mitt Romney has a portion of his fortune stored in offshore accounts, according to an ABC News report tonight that is stoking calls for him to release his income tax returns. The former Massachusetts governor has as much as $8 million invested in at least 12 funds listed on a Cayman Islands registry, according to the ABC report. He also has an investment valued at between $5 million and $25 million that securities records list as having been housed offshore in the Caymans.