Partisanship creates division among political parties and it is very difficult to come into terms or get an agreement on any proposal because neither side wants to lose.
With this scenario, the President needs to mobilize the members of his party to make things work in Congress. A polarized political situation makes it difficult for the President to pass hiss initiatives in Congress, and congressmen find difficult to pass theirs too for the Presidency's faculty to exercise his veto. Then, the country is in some king of paralysis. None of them have a "free pass" to approve nothing.
In this case, the President travels to the places where their party won the election to ask for the support of partisan voters instead of common citizens.
