"We think of Johnson as the person who ran roughshod over Congress. He knew how to get what he wanted, and he had no hesitation about steamrolling members who stood in his way. If they did, he gave them "The Treatment," where he hovered over them until they said yes. But that myth belies the centrality of good legislative conditions to Johnson's success. Many of Johnson's greatest moments as president came after the election of 1964. Republicans were demoralized by the defeat of their presidential candidate, Barry Goldwater, and scared to look as conservative as him. Democrats commanded massive majorities (295 in the House and 68 in the Senate), with liberals controlling the balance of power. After the 1966 midterm elections, when the conservative coalition of southern Democrats and Republicans regained their power, Johnson was far less effective."

http://www.vox.com/2015/1/17/7558391/lyndon-johnson-facts