Will Romney's Taxes Dog Him Until November?

And what other primary attacks will Democrats successfully revive? "We've already discussed that!"

Back in January, when Newt Gingrich was hammering Mitt Romney for financial secrecy and challenging him on a daily basis to release his tax returns, one senior Romney aide reached for a silver lining to the attacks.

Echoing the punditocracy's conventional wisdom, the aide insisted to BuzzFeed, "When these things get litigated in the primaries, it's very difficult to bring them up in a general election. It's like, 'We've already discussed that.'"

Ten weeks later, with Romney now the presumptive nominee, that theory is being put to the test. The Obama campaign is aggressively working to revive the issue of Romney's investments, and once again, Romney finds himself facing calls to release more tax returns.

The success of the campaign — which follows a Washington Post report that Romney is using a loophole in federal ethics law to avoid disclosing some investment holdings — remains to be seen. Democrats launched a #WhatsRomneyHiding Twitter campaign on Friday, only to watch it be hijacked by conservatives. Meanwhile, the Washington Post story has bounced around the blogosphere with some proficiency, and made its way into the cable news conversation.

But if the storyline continues to gain traction after the holiday weekend, and in the heart of tax season, it could signal that other hard-fought primary battles — like the candidate's record at Bain — will find new fronts in the general. Only this time, he'll have a much tougher opponent.

As the Romney aide put it in January, "As soon as Mitt Romney’s the presumptive nominee, there’s every reason to believe the Democrats are going to drop a massive attack on him. So, who would you rather face? Barack Obama at this moment, or Newt Gingrich?"

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