For decades Democrats had an advantage with seniors but that trend completely reversed after Obama took office. Republicans now have a noticeable edge with voters over 65. Obama can get away with this in a Presidential election because at the same time Democrats have developed a huge advantage among young voters — but it has created a huge problem for Congressional Democrats in mid-term elections with much older turnout.
While there are several reasons for Republicans gaining a big edge with seniors during Obama’s tenure much of the blame has to be put on his aggressive push to make senior citizens’ lives worse by cutting Social Security benefits. Despite the idea being extremely unpopular Obama insisted on putting chained-CPI in his budget.