The baths may be washing the Frontline away. I prefer Advantage for just fleas, or K9 Advantix for fleas and ticks. Be sure to get the product from your veterinarian. Some of the online stuff is not what it is supposed to be!
Try giving your dog massages instead of baths. If there is doggy odor, try just warm water in a bucket, wiping well with wet washcloth, and then buffing dry with a towel.
Massages bring the skin oil up onto the fur where it needs to be, and that alone may be all the dog needs. If you do sponge baths, watch your timing so that you don't wash away the flea product. You may want to wash just the face. And again, water on a washcloth rather than immersing the dog in water.
All soap does is make water wetter! You can bathe an animal (or yourself, for that matter) without soap, and avoid some risk of overdrying skin, causing reactions in dog skin--which is as sensitive as human lung tissue!--it really works well.
I believe you are also supposed to not put on the flea product right after a bath. It needs a bit of skin oil in order to distribute well on the body. And be sure not to use it more often than once a month.
If you have a cat, be sure to use the correct flea product on the cat, too. Many of the fleas in our homes are CAT fleas! I learned this one the hard way!
-----
Kathy Diamond Davis, author, "Therapy Dogs: Training Your Dog to Reach Others," 2nd edition, and the free Canine Behavior Series articles at http://www.veterinarypartner.com/Content.plx?P=SRC&S=1&SourceID=47
