They put their case forward that they could achieve left-wing policies, such as higher taxes on the rich and rent caps.
Mr Laschet strongly warned voters that a German government involving the far left would be an “extreme threat” for Europe.
He condemned his rival Olaf Scholz, the SDP’s leader, for refusing to rule out a coalition with the Left party.
The SDP’s are narrowly leading in the polls as the CDU trail 4 points behind them according to Politico.
Mr Laschet believes the SDP would try to form a government with the Greens and the Left if the figures worked out.