They find ways of working together

“It is a misfortune incident to republican government, though in a less degree than to other governments, that those who administer it, may forget their obligations to their constituents, and prove unfaithful to their important trust. In this point of view, a senate, as a second branch of the legislative assembly, distinct from, and dividing the power with, a first, must be in all cases a salutary check on the government. It doubles the security to the people, by requiring the concurrence of two distinct bodies in schemes of usurpation or perfidy, where the ambition or corruption of one, would otherwise be sufficient.” – James Madison, “The Federalist LXII”