In one of his most prominent breaks with political convention, President Donald Trump went on twitter in July mentioning his "complete power" to pardon, which many observers understood as an early claim that he can pardon himself and potentially anyone else who faces legal jeopardy from the current investigation into Russian collusion by special counsel Robert Mueller.
The result was a debate as to whether he actually has the power to self-pardon. A number of respected legal scholars have argued that his pardon power is vast and could include a self-pardon. But Trump's pardon threats may have created a bigger problem for himself and his team. The pardon power does have limits – it doesn't affect state and local law violations. And if Trump and the Republicans think that Mueller or Congressional investigation committees are dangerous, he should be prepared for a group of potentially even more ferocious actors on the political stage – the states' Attorneys General and local district attorneys.
These legal officers are able to look at which state laws the Trump campaign may have violated during the campaign. Thanks to the federal structure of government, a good portion of the federal government's laws are duplicated on the state level. In other words, you violate a federal law, there is a good chance that you are also violating a similar state law. Since the Trump campaign was a 50 state organization, and Trump himself has homes and significant business interests in New York, New Jersey and Florida, he may quickly find himself under multiple state investigations.
Being able to play a major role in an investigation of a sitting U.S. president – especially one as controversial and disliked as Trump – could be a political goldmine for a Democratic attorney general. Mueller has already brought New York's ambitious AG Eric Schneiderman into the investigation of the finances of Trump's former campaign chairman Paul Manafort, possibly in part to immunize against a presidential pardon.