Final answer:
Roosevelt's repetition of the phrase emphasizes the full support of citizens in both parties for his policy.
Step-by-step explanation:
The effect of Roosevelt's repetition of the phrases "by an impressive expression of the public will and without regard to partisanship" is to emphasize that his policy already has the full support of citizens in both parties. By repeating this phrase multiple times, Roosevelt is trying to convey to the public that his policy is a bipartisan effort, supported by both Republicans and Democrats. This repetition helps to reinforce the idea that his policy is not partisan, but rather a united effort for the benefit of the nation.