Organizing a 10 day tour of NE in July. I want to fly into Providence, head to Newport for a day or so then drive to Cape Cod for a few days then up to Boston and Finally head to Portland, ME for a day or so and fly out of there. Any suggestions or ideas? Is this itinerary doable? What spots on the itinerary are a must see? I want to get a Boston Go pass and def see the Nubble lighthouse in Portlamd but anything else is flexible.

The Nubble Lighthouse is in York, Maine , not Portland.

If you said more about what you like to do, it would help.
Cape Cod would be better mid week as July weekends are very busy. Definitely do not plan to arrive there on Friday eve or Saturday morning, or leave on Sunday unless you are prepared to monitor traffic.
I like the outer cape best, but, again it depends on what you want to do.

If you are interested in history, you should walk the Freedom trail when you are in Boston.

I agree with all that jubilada said and if you don't have lodging on the Cape yet, you need to get it asap.

Do try to time it so that you are on the Cape mid week and in Boston on the weekend. You don't mention if you are flying into and out of Providence or into Providence and out of Boston. If the later, then ditch the car and do Boston last.