Romney is hated by GOP Voters.
No Party ground game
Where would Mitt get 10 Billion Dollars?
Hillary has 2 Billion plus the whole democratic party.
Mitt would start with nothing
Romney has put out trial balloons about 4 times during the last 2-3 years, and they crash like lead balloons.
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Notice how none of the retreads from 2008 and 2012 got much traction in 2016. They are all old news.