Simplify the following text for a Grade 9 native English-speaking person.
Original: He was mainly responsible for bringing the whole political weight of the SPD to bear against Helmut Kohl and his CDU party , rejecting bipartisan cooperation that had characterized German politics for many years .
Simplified: He was mainly responsible for bringing the whole of the SPD against Helmut Kohl and his CDU party , instead of cooperating with the CDU .