Background
Same electric charges always repel each other, without exception. Opposite charges always attract.
An atomic nucleus with multiple positive charges must therefore generate tremendous forces to blow it apart. But many atomic nuclei are stable and can survive for decades or even billions of years without blowing apart.
Therefore there must be a more-powerful attractive force that holds them together in opposition to this repulsion.
This logic is ironclad and there cannot be any other way to look at it. The nature of this force was theorized to come from meson exchange. Then there were theories that attribute it to something separate from electric charge. It became convenient to imagine eight different color charges, and many complications were built which allow the theory to fit a great deal of experimental data. There is no possible alternative approach.
Or is there? Could there be another way to hold a nucleus together, that would involve different starting assumptions, that has not yet been disproven? Have there been other approaches which have been disproven?
Here's the sort of thing I'd be interested in
I make no claim that any model along these lines would work, but I could imagine that something vaguely like this might work.
Imagine that sometimes when a neutron and a proton are very close, they behave like two protons with a negative charge halfway between them. Then both of them are attracted to the negative charge four times as much as either of them is repelled by the other. So there is reason for deuterium to stay together.
Imagine that an alpha particle consists of four positive charges and two negative charges. The positive charges could form a square, with the negative charges above and below the center of the square. At some perpendicular distance for the negative charges, all six would be attracted more than repelled.
Each alpha particle might bind to other alpha particles -- a positive charge from one might be close to a negative charge from another. They might build like crystals.
A low-energy nucleus might be very much like an ionic crystal, and each component would have characteristic vibrations. Given higher energy inputs, a nucleus might split along cleavage planes, or start to "melt".
It would be interesting to do without the theorized strong force. But we would still need something more than simple electric charge. Large crystals depend on atoms to have excluded volume. Their attractive forces can't simply pull them together into a point. Protons would need a way to keep them from overlapping even when the forces that pull them together are always stronger than their charge repulsion.
Links
electromagnetic or gravitational spin might create strong force
Pairs of spinning charges create standing waves that hold them together
Color theory fits the known data so it is correct
Gluon theory proves that nucleons cannot ever form crystal structures
The Bottom Line
Again, I do not claim that any model along these lines could fit the observed data about atomic nuclei. Nor do I claim that it can't. I have not noticed any alternative to the theoretical strong force that's easier to understand, and I want to hear about any alternatives.