Affair is the go-to excuse for the coup plotters overly frequent communications.
This is what I have thought also. I have always wondered why Trump makes such a big deal out of calling them lovers in his tweets and at rallies when their is no actual evidence of that. PDJT usually has a reason.
Although there haven't been any texts released that would confirm it, there is congressional testimony by Strzok's boss Bill Priestap that there was at least an appearance of a relationship.