What role did compromise and negotiation play in the constitutional convention? contrast that with modern politics?

There was a significant amount of compromise and negotiation in during the constitutional convention. In order to set up the republic, representatives from all of the democracy gathered to dispute and discuss issues. One of the most contentious elements being slavery in the country. As such, negotiations led the the participants, to work further to balance state vs. federal rights. Often allowing for compromise to allow states to decide the issues that affected them most. 

Today's politics appears to be often one-sided and put forth as a "for us, or against us" type mentality. Meaning there is little room for negotiation or adjusting policy. Of course the inclusion in the constitution the separations of powers and the system of checks and balances still maintains one of the best political systems humankind as witnessed by the example of over 200 years of peaceful transfers of power from governing authority to governing authority, even though disputes and disagreements regularly occur.