C177 pilot reported communication radios failing while being vectored for an instrument approach. Communications were reestablished with a backup radio and aircraft landed.

Narrative

We were in contact with ZZZ TRACON on XXX.X and navigating via VXXXWe acquired ZZZ information Romeo (ZZZ)Close to ZZZZZ intersection we received a vector to 180 degreesThe GTN 750 display began flickeringWe switched to the second radio which began showing symptomsWe found that multiple instruments were having difficulty and determined we were losing electrical powerWe located and connected the back-up hand-held radio and re-established communication with ZZZ TRACON on XXX.XConcerned that if we lost the iPad and handheld com we would be blind; we [requested priority handling]Communication rapidly deteriorated and we lost contact with ZZZ TRACON.At this point only the back-up iPad appeared reliable.Concerned; we opted to navigate direct ZZZZZ1 and try contacting ZZZ Tower directly.We were able to contact ZZZ Tower and proceeded to execute the ILS XXR approachUpon reaching approximately 1;300 feet; we broke out of the cloud layer and were able to follow the information Romeo instructions to circle North and enter left traffic for runway YYLWe landed on YYL with no further incidents and taxied to parking.We contacted the Tower and thanked them for their assistance.