The Democratic Party didn't run for the Presidency, President Obama ran for the Presidency. At some point, the President has to be accountable for the policies he ran on as a candidate and then followed through on as President.
They are Obama's policies.
Reagan's final policies weren't exactly as he proposed, but they were pretty close to what he wanted. They became his political responsibility.
Same thing with Obama. They might not be identical to his perfect vision of governance, but they are close enough to tag his name to them politically.