As National Secretary, Lewis emphasized organization over ideology and forging links to unions.
He worked to moderate the party's image and downplay the Regina Manifesto's more radical language, which seemed to scare off moderate voters.
The offending language included "No CCF government will rest content until it has eradicated capitalism and put into operation the full programme of socialized planning".
Lewis, federal leader M.J. Coldwell, and Clarie Gillis would spend the next 19 years trying to modify this declaration, finally succeeding with the 1956 Winnipeg Declaration.

At the 1944 CCF convention, Lewis won a concession "that even large business could have a place in the party – if they behave."
Rather than opposing all private enterprise, Lewis was concerned with preventing monopoly capitalism.
 He passed a resolution reading "The socialization of large-scale enterprise, however, does not mean taking over every private business.
 Where private business shows no signs of becoming a monopoly, operates efficiently under decent working conditions, and does not operate to the detriment of the Canadian people, it will be given every opportunity to function, to provide a fair rate of return and to make its contribution to the nation's wealth."
This resolution allowed for a mixed-economy that left most jobs in the private sphere.

Lewis did not share the desire of some members to keep the CCF "ideologically pure", and adhered to the Bundist belief that "it was better to go along with the masses in a not totally correct direction than to separate oneself from them and remain 'purist'."
However, the CCF was as much a movement as it was a political party, and its own members frequently undermined it with radical proclamations.
 Lewis criticized the British Columbia CCF for such comments, saying "... what we say and do must be measured by the effect which it will have on our purpose of mobilizing people for action.
 If what we say and do will blunt or harm our purpose ... then we are saying and doing a false thing even if, in the abstract, it is true ... When, in heaven's name are we going to learn that working-class politics and the struggle for power are not a Sunday-school class where purity of godliness and the infallibility of the Bible must be held up without fear of consequences."

David Lewis was the party's "heavy", which did not help his popularity among CCF members, but after witnessing what he considered to be the European left's self-destruction in the 1930s, he was quick to end self-immolating tactics or policies.
 He would tolerate some criticism of the party by its members, but when he believed that it rose to self-mutilation, he suppressed it ruthlessly.
 This was most apparent when Lewis attacked and discredited Frank Underhill and his handling of Woodsworth House.
 Early in Lewis' career, Underhill was one of his mentors; this did not matter when Woodsworth House was stricken with financial difficulties in the late 1940s.
Lewis was quick to blame and then discharged Underhill and the rest of the Woodsworth executive of their responsibilities.
It was an unfortunate event that cost the CCF in the academic and intelligentsia world.
To sum up Lewis' reign, discipline and solidarity were paramount.
 There had to be limits to discussion and tolerance of dissenting views.
As National Secretary, Lewis emphasized organization over ideology and forging links to unions. He worked to moderate the party's image and downplay the Regina Manifesto's more radical language, which seemed to scare off moderate voters. The offending language included "No CCF government will rest content until it has eradicated capitalism and put into operation the full programme of socialized planning". Lewis, federal leader M.J. Coldwell, and Clarie Gillis would spend the next 19 years trying to modify this declaration, finally succeeding with the 1956 Winnipeg Declaration.
At the 1944 CCF convention, Lewis won a concession "that even large business could have a place in the party – if they behave." Rather than opposing all private enterprise, Lewis was concerned with preventing monopoly capitalism.  He passed a resolution reading "The socialization of large-scale enterprise, however, does not mean taking over every private business.  Where private business shows no signs of becoming a monopoly, operates efficiently under decent working conditions, and does not operate to the detriment of the Canadian people, it will be given every opportunity to function, to provide a fair rate of return and to make its contribution to the nation's wealth." This resolution allowed for a mixed-economy that left most jobs in the private sphere.
Lewis did not share the desire of some members to keep the CCF "ideologically pure", and adhered to the Bundist belief that "it was better to go along with the masses in a not totally correct direction than to separate oneself from them and remain 'purist'." However, the CCF was as much a movement as it was a political party, and its own members frequently undermined it with radical proclamations.  Lewis criticized the British Columbia CCF for such comments, saying "... what we say and do must be measured by the effect which it will have on our purpose of mobilizing people for action.  If what we say and do will blunt or harm our purpose ... then we are saying and doing a false thing even if, in the abstract, it is true ... When, in heaven's name are we going to learn that working-class politics and the struggle for power are not a Sunday-school class where purity of godliness and the infallibility of the Bible must be held up without fear of consequences."
David Lewis was the party's "heavy", which did not help his popularity among CCF members, but after witnessing what he considered to be the European left's self-destruction in the 1930s, he was quick to end self-immolating tactics or policies.  He would tolerate some criticism of the party by its members, but when he believed that it rose to self-mutilation, he suppressed it ruthlessly.  This was most apparent when Lewis attacked and discredited Frank Underhill and his handling of Woodsworth House.  Early in Lewis' career, Underhill was one of his mentors; this did not matter when Woodsworth House was stricken with financial difficulties in the late 1940s. Lewis was quick to blame and then discharged Underhill and the rest of the Woodsworth executive of their responsibilities. It was an unfortunate event that cost the CCF in the academic and intelligentsia world. To sum up Lewis' reign, discipline and solidarity were paramount.  There had to be limits to discussion and tolerance of dissenting views.
David Lewis (politician)