A bipartisan duo in the Senate has been garnering attention for a pitch aimed at shoring up the solvency of Social Security.

The idea, pushed by Sens. Bill Cassidy (R-La.) and Tim Kaine (D-Va.), calls for investing $1.5 trillion over the next five years into an investment fund that would then be given 70 years to grow.

“It is something to save Social Security, and to save the benefits flowing to the people, frankly, will either already depend on them or will depend upon them going forward,” Cassidy told The Hill last month.