Because a razor-thin margin of the people dumb enough to approve of trump but smart enough to know where their healthcare bread is buttered just might be enough (depending on the area, of course):

Some strategy math:

Around 45% of people approve of Trump

Only 30% think Repubs are better on healthcare

So, 15% of the pop agrees with us on healthcare but disagrees about Trump.

Talk about healthcare not Trump.

Even a 1% swing in voting equals about 15 more House seats.

— The Hoarse Whisperer (@HoarseWisperer) October 25, 2018