Just dig down as deep as you possibly can to get the root, try to keep a clump of soil intact. I've done it successfully with a mature plant, but it did set it back a lot.

But wait until spring! It's much too late in zones 5 or 6 to transplant perennials.

We've been having unseasonably warm weather, but I will wait for spring!

Thank you both for your suggestions.

Tom,

Can you BELIEVE the weather we've been having?? Get ready for the temps to go below freezing Tuesday night. This Halloween is the first in 5 years where we haven't had snow on the ground...or actually snowing. Anyway, I would wait til Spring, too.

Yep, wait until Spring, dig out as much around the roots as you can (be careful of a long taproot which might be growing sideways away from the plant), try not to break the taproot, and then be prepared for a season or two of no flowers. I moved mine a few years ago, and it didn't die, but it took a couple of years for it to bloom again - though when it did it was glorious - well worth the wait.