"[Throughout the month], many people voted [in regard [to the new proposal]]".

Altogether, there are 3 preposition phrases:

1. "throughout the month".
2. "in regard to the new proposal".
3. "to the new proposal".

As you can see, the last PP "to the new proposal" is part of the larger PP "in regard to the new proposal". It's a PP within a PP!



PaulM