WASHINGTON — Stepping up Democratic efforts to shield the Russia investigation, Senate Minority Leader Chuck Schumer said Sunday he would seek to tie a measure protecting special counsel Robert Mueller to must-pass legislation if acting attorney general Matthew Whitaker does not recuse himself from oversight of the probe. Schumer pointed to Whitaker’s “history of hostile statements” toward the Mueller investigation. “If he stays there, he will create a constitutional crisis by inhibiting Mueller or firing Mueller.