The biggest reason is the rapidly changing demographics in this country fueled by immigration, legal and illegal, and high minority birthrates. Immigrants and minorities vote Democrat. By 2019 half of the children 18 and under will be minorities as defined by the USG and by 2042 half of the country will be minorities.
Right now government at all levels controls 42% of the GDP. Almost one in every two Americans receives a government check.
Now she's falling and she can't get up. Physically she'll be an even bigger hot mess 4 years from now. Don't underestimate the general public’s distaste of a heavyset 70 year old woman representing their nation.