Sanders' overall aim is to have the Democratic Party platform reflect his agenda. True, candidates often ignore the party platform. But it remains a measure of the party's priorities and values.
Sanders first step will likely be direct negotiations with Clinton -- to probe what she is prepared to champion. He'll want commitments on, for example, an executive order granting preference in government contracts to companies that pay a living wage with solid benefits, or on ending the tax loophole that lets hedge fund billionaires pay lower tax rates than their secretaries.
Sanders has already moved Clinton left on trade issues. She has come out against Obama's Trans-Pacific Partnership deal. She has also promised to sign a $15 an hour minimum wage bill and says she would never again allow Wall Street to threaten Main Street. She's talked about regulating fracking tightly enough to make it virtually impossible. Her platform on reforming money in politics is essentially identical to Sanders'.
But Sanders is still pressing her to support tuition-free public college, which she has mocked in the past. A broader program along these lines would certainly help her with millennials, who have voted against her in overwhelming numbers.
Depending on convention rules, Sanders is likely to have enough delegates to bring some of his signature proposals before the entire convention. These might include Medicare for all, a carbon tax, a ban on Super PACs in Democratic primaries and breaking up the big banks. Many of Clinton's delegates favor one or more of these proposals.
The argument in the Republican Party has focused more on Trump's character than his policies. The Democratic debate in Philadelphia will be on substance -- the policies and priorities of the party and the direction of the country.
That contrast alone is likely to give the nominee a boost headed into the general election.
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