Is a blue wave coming for the Democrats?

23: It’s the number of seats the Democrats need to flip to win back the House in the midterm elections. It’s not an impossible number, but there are a few factors to take into consideration before asking whether a "blue wave" is coming. From historical trends, to President Trump's approval rating to strategy and the great unknown, MSNBC's Steve Kornacki and NBC Left Field set up some context for the upcoming 2018 midterm elections.