Trump's team along with some specialized citizen groups have been performing various types of analysis.  And one of the ways they're finding -- which slashes into claims of election integrity -- is where registered voters are numbering greater that the eligible adult population. 

Keeping the dead names on the lists eligible to vote, names over 100 yrs old, names of non-citizen immigrants, names with phony addresses like post offices, vacant lots, retail stores, etc. and other fictitious names have been some of the abuses which have occurred.

Quotes from the Michigan report: 

"There's about 1.8 million more [Michigan] registered voters than eligible voting-age citizens.

"nearly 2,000 are 100 years old or more and aren’t listed as known living centenarians."

"about 9,500 voters confirmed dead through the Social Security Death Index are marked in the state’s mail voting database as having returned ballots." 

A study by Judicial Watch reported that 353 U.S. counties in 29 states have voter registrations exceeding 100 percent of eligible adult citizens.

Michigan is important as its among the six swing states, decided with very small margins of votes.  It was decided by 146,123 votes, far lower than the 1.8 million registered voters of questionable authenticity.