Julian Zelizer : Democrats face a similar challenge . Midterm elections could change the balance of power in Congress . Zelizer : If Democrats win , they can force compromise ; if Republicans wins , it can torpedo Congress . He says midterms will be a stab at challenges and promises parties will win in 2016 . Zelizer : Elections will also offer a huge field for possible presidential candidates .
Julian Zelizer : Midterm elections could change the balance of power in Congress . Zelizer : If Democrats win , they can force compromise ; if Republicans wins , it can torpedo Congress . He says midterms will be a stab at challenges and promises parties will win in 2016 . Zelizer : Elections will also offer a huge field for possible presidential candidates .