Reagan/Crane 1980 might not have won.
Goldwater/Miller 1964 certainly didn't.
Would Cruz bring Trump votes he wouldn't otherwise win?
More votes than another running mate would?
Poppy was Reagan’s big mistake (other than amnesty). Trump will win by getting the base out, along with the independents and Reagan Democrats he already attracts on his own. Cruz also brings DC and Senate experience, without the tarnish of business as usual.