According to trends researched by Gallup, most Presidents lose seats in the midterm elections, but looking at numbers from 1946 through today, Commander-in-Chiefs with a 50%+ approval rating lose an average of 14 seats in the House of Representatives during midterm elections, while those with >50% approval lose an average of 36 seats.
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.
In general, though, the more popular a president is, the fewer seats his party loses, as presidents with approval ratings above 60% have averaged just a three-seat loss
Keep in mind that the 50%+ number is probably inflated as it includes a loss of 43 seats for Gerald Ford. That 1986 election was also the voter’s first chance to voice their disapproval regarding Watergate (taking out the Ford number would make the average -4).
On the other hand the <50% number is deflated. In 1978 Jimmy Carter’s approval was just below 50% (49%) and his losses reflected his relatively moderate approval. Without the Carter losses the average loss would be 40 seats.
Based on Gallup’ daily tracking poll Barack Obama’s approval rating has averaging 45% during the last two full weeks of tracking. Based on the numbers adjusted above, and the president’s low approval numbers , the GOP will gain the 40 seats it needs to retake the house.
Obviously this is just an historical trend, the GOP has to work hard in the trenches to make it happen, but it does show that it CAN happen.