I have a tub/tile joint that widens from virtually nothing to about a one half inch gap. This of course is at the front end of the tub and has water from the shower pooling at it. Originally it was grouted and then caulked on top but both have deteriorated and attempts to recaulk have failed. Should I put grout in the wide area of the joint between the tub and tile or just try to fill it with a lot of caulk?
Thanks

Where exactly is this joint, is it between the tub and the tile, is it vertical or horizontal?

The joint is horizontal between the tub and the first row of tiles on the wall at the front end (drain/faucet) end of the tub. The joint goes from negligible on the left side to about half an inch on the right side corner with the tub up against the wall on the right side if you are facing the drain.
Thanks for your interest

You can regrout if you want to, but you will have to use caulk on that joint. So - remove old grout and caulking completely.

Use silicone/acrylic mix of caulking. For the larger joint, put a first run of caulk on. You can use painter's tape to keep the lines straighter. Wait until that first application on the larger joint is dry before doing your finish joint. Take the painter's tape off only when the caulk is partially dry. Test the end of it if you have to.

Do NOT wait until the caulk is completely dry before taking off the tape. That won't do.

Do not use straight silicone. You can't apply more caulk over silicone so make sure your caulk states that you can reapply.