From NBC's Domenico Montanaro
This morning, we showed you some of the numbers we crunched on Senate races and how historically the Senate shift is much narrower than for the House in a president's first mid-term.
Charlie Cook, one of THE smartest guys in the business on this, wrote us after we published arguing that it might be a better measure not to include, for example, 1946 -- Truman's first mid-term election after assuming the presidency a year earlier when FDR died.
"The way I look at it, it is a party's first midterm election after taking office, or if a party holds onto the White House after eight years (e.g. 1988), the next midterm election," Cook writes. "I don't make a distinction between the Kennedy and Johnson elections; Johnson simply carried over the Kennedy Administration, agenda, etc. So by my reckoning, 1966 is a second-term, midterm election. Part of it is being a purist, the other part is that making exceptions creates more problems. It's rather extraordinary for a new president to win the kind of election (37 House seats gained) that LBJ/Dems did in 1964 (in part due to Kennedy's death), thus setting Dems up for huge 1966 midterm (47 House seats) losses. It bends the numbers a lot."
When you take those out -- '46, '66 and '74 -- The Cook Report finds an even lower average loss of 0.4 seats for the president's party from the prior year.
If you take out 1946 and 1974, and include 1966 and calculate from the prior election year (not the previous Congress), the average loss is 1.3. Not a big difference. Point is, the historical trend for the Senate does not hold as compared to the House.
Here are the numbers with '66, but not '46 or '74 (from the previous election cycle):
1954: Eisenhower -1 (48 senators in 1952 to 47 in 1954)
1962: Kennedy +3 (64 in 1960 to 67 in 1962)
1966: Johnson -4 (68 in 1964 to 64 in 1966)
1970: Nixon +2 (42 in 1968 to 44 in 1970)
1978: Carter -3 (61 in 1976 to 58 in 1978)
1982: Reagan +1 (53 in 1980 to 54 in 1982)
1990: H.W. Bush -1 (45 in 1988 to 44 in 1990)
1994: Clinton -10 (57 in 1992 to 47 in 1994)
2002: W. Bush +1 (50 in 2000 to 51 in 2002)
Avg. Loss: 1.3