"To repeat the assertion" means to state or express something again. It indicates that the speaker or writer wants to emphasize or reinforce their previous statement. Full definition
It is now even more clear that wind and solar will not be able to compete in the marketplace for many years if not centuries, contrary to repeated assertions by the environmental left. (carlineconomics.com)
It has repeated the assertion in a recent wave of material from leadership to rally the troops in the name of unity and union survival. (laschoolreport.com)
All you can do is repeat the assertion like the little sheep you are. (religion.blogs.cnn.com)