Of the 25 current races, the Republicans have secured 4, and the Democrats have secured 1. there are currently no Libertarians or Independents in office.
The Democrats would have to win all 19 races they are filed in, to secure a 1-seat majority.
There are 4 Independents challenging for senate seats this year. They could come into an important role if they are successful and the Democrats fall just short of an electoral miracle. The same is true for the Libertarians. There are 2 Libertarians challenging this year.
The senate leader has been Brian Bingman. His seat is open and there will, therefor; be new leadership.