This explainer by the person who ran Medicare and Medicaid services shows why the GOP health care plan is a disaster

In a series of 21 tweets on Friday, Andy Slavitt spelled out a doomsday scenario of how the Republicans’ new American Health Care Act would hurt the people who can least afford its increasing premiums and less access to tax credits: the aging, elderly and the poor. Slavitt should know—from 2015 to 2017, he ran the Centers for Medicare and Medicaid Services.

Slavitt noted that in the United States, half of nursing home care is covered by Medicaid. “This means more aging parents moving into basements” and greater poverty for seniors, he tweeted.

The GOP bill’s tax-credit structure would make health insurance less affordable for millions of people, particularly those over 55, Slavitt wrote in a recent Washington Post column. But one of the worst long-term effects is its erosion of Medicare and Medicaid, just when Obamacare had begun to breathe new life into the financial longevity of these essential government programs, which have helped dramatically reduce poverty over the years specifically among the elderly.

The GOP bill also likely would force many workers to put off retirement in order to afford health care coverage when they begin to need it most in their lives.

Below are some of Slavitt’s key points. You can read the entire explainer here to see just how badly Republicans have scammed some of their biggest constituents. If you’re still on the fence about how dreadful this health care plan is, take Slavitt’s advice: Think about your parents and grandparents.