There is no need to place the country under martial law. The targeted use of military assets, Marines, Special Forces, is all that would be necessary to arrest high-level officials, secure evidence such as voting machines, and put down any riots that occur. There are also plenty of federal agents that can assist, or do the job themselves.
Probably. Just like all the other 'characters' that are attempting to destroy the board, like 'barkeep' and OSS.