Currently, there are 52 Republicans in the Senate, 46 Democrats, and two Independents who caucus with Democrats (Bernie Sanders and Angus King). It takes three Republicans (assuming Democrats stick together) to defect from the party position in order for Republicans to lose on an issue that requires a majority. Democrats can filibuster in some cases to block legislation, but there are many ways for Republicans to get around that.
2016 presented a favorable Senate map for Democrats — with more Republicans up for reelection than Democrats –but Democrats picked up only two seats. 2018 will be much harder as more seats are up for reelection or will be open (with no incumbent) that currently are held by Democrats.
Identify good Senate candidates.
Identify vulnerable Senators in both parties and pressure them to support our positions.