Simplify the following text for a Grade 9 native English-speaking person.
Original: In 1987 , Rau tried to become chancellor of Germany for the SPD , but his refusal to contemplate forming a coalition with the Green Party meant he could not win the elections against Helmut Kohlâ s Christian Democrats ( CDU ) .
Simplified: In 1987 Rau tried to become chancellor of Germany for the SPD , but lost to Helmut Kohl 's Christian Democrats ( CDU ) .