In my bathroom sink there is standing water- but only below the stopper. The water drains a bit slow but doesn't back up at all. I have cleared all debris and flushed the drain with a Drano type cleaner and it didn't help at all. The worst part is that the water smells aweful. What is your advice?

I would stay away from draino in a bathroom sink.. Too many people burn themselves with chemicals when it is pretty easy to open these pipes. Put a bulet under your P trap and remove both nuts on the trap. You will be able to dump the trap and see if there is any blockage. No blockage? Try rodding the drain where it enters the wall/floor. You definitely have some blockage.

I would stay away from draino in a bathroom sink.. Too many people burn themselves with chemicals when it is pretty easy to open these pipes. Put a bulet under your P trap and remove both nuts on the trap. You will be able to dump the trap and see if there is any blockage. No blockage? Try rodding the drain where it enters the wall/floor. You definitely have some blockage.

I tried both of these things and although the water ran freely for the first couple uses and I thought I had it all figured out the standing water returned. This time, not stinky or gross, but standing water just the same. I can't say I'm not frustrated doing all of that for no result.:(

If your p trap is clear then your blockage is after the trap, possibly where the tail pieces goes into the verticle drain in the wall. Did you rod with a actual rodding tool or just a coat hanger? A rodding tool will be able to snag debri on its spring like head. Next big step after this is to rod down the roof vent. That is not for most home owners.