Assuming the two independents won re-election and continued to caucus with them, Senate Democrats needed to win a net gain of two Senate seats to win a majority.[lower-alpha 5] Including the two independents, Democrats held approximately 74 percent of the seats up for election, the highest proportion held by one party in a midterm election since at least 1914.[15] Prior to the 2018 elections, Nate Silver of FiveThirtyEight wrote that Democrats faced one of the most unfavorable Senate maps any party had ever faced in any Senate election. Silver noted that ten of the seats Democrats defended were in states won by Donald Trump in the 2016 presidential election.[16][17] Meanwhile, the Class I Senate seat in Nevada was the lone Republican-held seat up for election in a state that had been won by Democratic nominee Hillary Clinton in the 2016 presidential election.[18] Silver predicted that even a nine-point victory in the nationwide popular vote for Congress would not be enough to give Democrats a majority in the Senate.[16] Some observers speculated that Republicans might be able to pick up a net of nine seats, which would give them the 60-seat super-majority necessary to break filibusters on legislation.[19]