Democratic presidential candidate Hillary Clinton and Republican presidential candidate Donald Trump. (EPA/Justin Lane/Andrew Gombert)

Republican presidential candidate Donald Trump can seem difficult to pin down on taxes, particularly on those for the rich. His printed tax plan quite clearly says he would cut the top income tax rate by a lot, along with the corporate rate and the estate tax — all moves that would absolutely benefit high earners. But in the pivot to the general election, Trump is also saying those details are negotiable and that the middle class remains his biggest concern.

There are six months left until the election, which leaves Trump plenty of time to update his white paper and pick whatever tax details he thinks would both help the economy and help him defeat Democratic candidate Hillary Clinton. On Monday, Clinton made the first of what figures to be many attempts to stop that evolution — by pinning Trump to the details of his plan, as first released, and using those details to cast him as a friend of millionaires over typical workers.

Clinton policy aide Jake Sullivan and Gene Sperling, a former head of President Obama's National Economic Council, attacked the Trump plan in a wonky afternoon conference call that was filled with distributional analyses from the Tax Foundation and Tax Policy Center. They emphasized projections, from those groups, that Trump's plan would deliver far more benefits to the rich than to most American workers, that it would swell the federal budget deficit dramatically, and that it does not even contain the modest downsides for hedge fund managers that Trump claims it does.

Sperling called the Trump plan “the most risky, reckless and regressive tax proposal ever put forward by a major presidential candidate" and said it contained a tax cut for millionaires that was so large, the money could otherwise be put to use shoring up Medicare and Social Security solvency for 75 years.

Sullivan said the plan was “exposing to the world just where Mr. Trump’s economic priorities lie” — with the rich, not the middle class.

Trump's Republican rivals attacked his policy proposals in the primaries, and they never had much luck, in part because Trump kept his proposals vague or fungible or both.

Clinton apparently believes she can succeed where they failed, in part because her attack — on millionaires vs. workers — has broad appeal (including among Trump's base voters). But she also appears to believe that to change voters' perspective on Trump, away from Middle Class Champion and toward Friend of the Fat Cats, she must press the case early and often.

“It’s not a matter of us coming out today to do this," Sullivan said. "We’ll be doing this every day from now until the election.”

That should keep the tax-policy analysts busy, if nothing else.

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