That really has to be the Democratic message on this issue-- "House Republicans Side with China's Rich American Friends".
President Obama should acknowledge publicly that China has a weak-renminbi policy, that this harms American manufacturing employment and this needs to change. He can be milquetoast otherwise, sounding sad that Chinese foot-dragging has led us to this and wishing it could all be worked out in a respectful manner. But he needs to imply that he favors action.
Congressional Democrats, on the other hand, have no reason to pull their punches. They should loudly point out that the Republicans are again siding with their rich friends who make money importing cheap goods from China, wealthy interests that have little in common with the American people.
China has domestic political incentives to let the renminbi gather strength (a stronger renminbi makes imports into China cheaper at a time when inflation is a tremendous concern.) The public long-term policy is that eventually the renminbi will float without manipulation. Making a stink is likely to help those in China who want this to happen more quickly. If Europe and Latin America and India get on board, all the better.
(I should mention that I get paid in renminbi and buy more imports than most people in China, so a better exchange rate for the renminbi is helpful to me, personally.)