( CNN) It will take more than a devastating diagnosis to keep John McCain out of the hot of political battle.

The Arizona senator makes a poignant return to the Senate on Tuesday, less than a few weeks after discovering he has an aggressive sort of brain cancer, just in time to boost tricky GOP vote math on the wobbling bid to replace Obamacare.

McCain’s return comes as he considers treatment options for the most recent battle of a lifetime of military gallantry and political combat that has constructed him one of America’s most enduring public figures.