How Much You Can Change the Strength of Electromagnetism?

If the strength of electromagnetism was slightly larger or smaller, it would mean that atoms would be slightly smaller or larger. This probably would not preclude atoms from being formed or chemistry from taking place. Life could probably still exist, but it would just be different. And therefore fine tuning argument fails ind some way, somehow. But i love athe claim is just thrown out there with no reference to any scientific literature about what changes in power can do. He's just throwing it out and ignoring everything else that tatthat constance involves.