In order for Republicans to take control of Congress, 2 accomplishments must occur. First, since there are currently 255 Democrats and 178 Republicans in the House, Republicans must take 39 Democratic seats to have a House majority. According to the latest polls of each race, Republicans are favored to take 45 Democratic seats. Additionally, there are over 40 other Democratic Representatives who are in toss-up races, so Republicans could potentially have a record day in the House. Among the past 20 midterm elections, FDR holds the record for the most Representatives turned over to the other party, when the Democrats lost 72 seats in 1938.
Second, since there are currently 59 Democratic Senate seats and 41 Republicans, Republicans must take 10 Democratic Senate seats in order to have a Senate majority. After a careful analysis, Left and Right News projects Republicans to gain only 7 Senate seats – thereby resulting with a Democratic Senate majority. Still, midterm elections average a gain of 3 Senators for the party not holding the presidency, so a shift of 7 Senators is an above average shift in the Senate. The record for the most Senators turned over to the other party among the past 20 midterm elections belongs to Harry Truman and Dwight Eisenhower, when each of them lost 12 Senators in 1946 and 1958, respectively.
Regardless of the likely outcomes, the magic numbers for Republicans are 39 in the House and 10 in the Senate.