There is only one reason for Mueller to issue a subpoena...He has hit a
dead end and knows his entire investigation will be shut down by the SCOTUS
or limited to just collusion.
So he'll issue the subpoena and when the SCOTUS closes him down the Dems
will use that as a rallying point for their voters to fight to retake the Senate, to control the potential 4 Supreme Court nominations Trump could make between
now and 2024. Ginsburg, Kennedy, Breyars and Thomas.
If Trump replaces all of them it's be 7-2 conservative for 25 years and 6-3 conservative for 35 years.