MARSHALLTOWN, Iowa (AP) — Bernie Sanders insists he feels better than ever less than a month after heart surgery, but his return to the campaign trail this week sparked new questions about the unusually old age of the Democratic Party’s leading 2020 presidential candidates. The 78-year-old Sanders and 76-year-old Joe Biden suggest their age isn’t a major issue, but voters aren’t so sure. Gordon Lundberg is a 71-year-old retired Lutheran pastor from Ames, Iowa, and says candidates’ health is a key issue for him.