On a historical basis, the Democrats under Jimmy Carter suffered the slimmest seat loss of a party whose president was below 50% approval, losing 11 seats in the 1978 midterms. More recently, Bill Clinton in 1994 and George W. Bush in 2006 saw their parties lose enough seats in the House to turn party control over to the opposition party when they had less than majority approval.
The president’s party nearly always loses seats in midterm elections, regardless of how well the president is rated by the public. Since World War II, only Clinton in 1998 and Bush in 2002 saw their parties gain seats in a midterm. Both men had approval ratings above 60% at the time of those elections. However, the parties of the other three presidents with ratings above 60% (Eisenhower in 1954, Kennedy in 1962, and Reagan in 1986) lost seats.