You should be fine as long as you get all the roots and don't damage the tuber. I transplanted one this year that was 2 feet high and it survived. It withered a bit at first, but then it was fine. Move it later in the evening when it isn't hot...

The trouble is with dahlia....you plant A tuber...one.
In a few short months, what you have now is more than one.
You have maybe a clump of size and lifting it I'm sure would cause the plant and flowers to wilt badly.

Unless you can lift a sizable root ball and deposit into the its new home, I'm afraid your plants might suffer.
But hey....when there's need....