If I'm not mistaken, a full national declaration of martial law would require not only approval of individual state legislatures, but also the loyalty of the military and the National Guard in every state.
By bypassing laws and regulations, totally disregarding checks and balances now that mechanism is compromised, the bastard need not to declare martial law to spread terror.
How 50-80 years ago winning an appliance on TV used to be a big deal, like all the sudden the winner's household gets a massive jump into the space age because the appliances then must have been expensive.