CLEVELAND, TENN. — They were told to arrive early if they wanted to see a doctor, so Lisa and Stevie Crider left their apartment in rural Tennessee almost 24 hours before the temporary medical clinic was scheduled to open. They packed a plastic bag with what had become their daily essentials after 21 years of marriage: An ice pack for his recurring chest pain. Tylenol for her swollen feet. Peroxide for the abscess in his mouth. Gatorade for her low blood sugar and chronic dehydration.