After an election season that appeared too close to call up until votes were officially cast Tuesday, Republicans have officially retained the majority in the Senate. Now, with that support, Kentucky Sen. Mitch McConnell is expected to keep the top leadership job in the country’s highest legislative body.

Ahead of Election Day, forecaster FiveThirtyEight and other political handicappers including the Cook Political Report and the Rothenberg and Gonzalez Political Report predicted that the fight for control of the Senate would be decided along razor-thin margins. At that time, seven Republican seats were potentially in jeopardy with ratings as "pure toss-up races," "toss-up races leaning Democrat" or races that were only "leaning Democrat." Just one Democratic seat, the one left open by outgoing Senate Minority Leader Harry Reid of Nevada, was in play for Republicans to grab as a "pure toss-up," according to Rothenberg and Gonzalez. Democrat Catherine Cortez Masto ultimately won Reid's seat, but it wasn't enough to give them the Senate. 

Heading into Tuesday’s election, Democrats needed to pick up at least four seats to gain control of the Senate, assuming Hillary Clinton also won the White House (making Tim Kaine the tie-breaker vote). If they lost, the Democrats needed a five-seat pickup to fend off Republican legislative advances and keep bills from landing on the desk of a President Donald Trump. The math in 2016 favored Democrats, in general, as Republicans were defending 24 seats including several Senate seats in states that are reliably blue in 2008 and 2012.

Just a third of the Senate is up for re-election in any given election since the legislative body has six-year, staggered terms so that seats change between midterm and presidential elections. A staggered system also theoretically stabilizes the Senate since only a third of the legislative body can change in any given election.

Republican Roy Blunt won re-election to the U.S. Senate in Missouri, as did Republican Pat Toomey of Pennsylvania.