The last time we had a Senate divided at 50/50 was back in 2001. It only stayed that way until May of 2001 when Vermont Republican Sen. Jim Jeffords switched parties, giving Democrats 51 seats.
But, the make-up of the Senate was much less polarized than it is today. In 2001, 30 senators — 10 Republicans and 20 Democrats — represented a state that voted for the other party’s presidential nominee. … Today, just six senators — three Republican and three Democrats — sit in a state where their party’s nominee for president did not win. In other words, 20 years ago, many more senators had a political incentive to work with the opposite party. …
We also know that the two parties don’t just disagree on how to solve problems; they don’t even agree on the same set of problems. CONTINUED
Amy Walter, Cook Political Report