Today, they followed it up with this one:
(Click on the images for larger versions)
They're right: this is not about partisanship or pushing a political agenda - it is about the rule of law, and whether the President and the government are above the law or subject to it. And in a democracy, where there are checks and balances and where the government is politically accountable to the people, there can only be one answer to that question.
If you are American, you can send a letter to your Congressperson and Senator here.