washington republican democratic senators introduce two piece legislation thursday seek block president donald trump fire special counsel probe tie russia congress increasingly seek assert authority policy members congress party express concern trump might dismiss robert mueller special counsel appoint determine whether collusion 2016 presidential campaign moscow republican president may fire fbi director jam comey oversee investigation also recently criticize attorney general jeff sessions recuse probe sign mueller investigation intensify members congress seek protect special counsel appoint may 17. two source familiar matter tell reuters thursday mueller convene grand jury washington investigate allegations russian meddle source add grand jury subpoena issue connection june 2016 meet involve trump son son-in-law russian lawyer moscow deny effort influence election trump dispute allegations collusion associate russia bill allow judicial review decision terminate counsel make sure do reason cite regulations rather political motivation say republican senator lindsey graham co-sponsored one bill democratic senator cory booker second generally similar measure introduce republican senator thom tillis democratic senator chris coons coons tell reporters expect two group senators would work together seek co-sponsors party come single bill say discussions leaders senate judiciary committee hope would take bill step toward vote full senate measure introduce senate prepare leave washington august recess lawmakers return early september members congress include trump fellow republicans recently pursue legislation seek increase congress influence u.s. policy last week lawmakers vote almost unanimously sweep sanction bill give congress right review trump effort ease lift sanction russia trump sign bill law wednesday senators propose legislation protect special counsel trump