To put Mitchell's encouraging comments in perspective, while he did enter the 1982 US Senate race significantly behind in the polls (after being appointed to the Senate in 1980), by a week before the election he was up by at least 4 points according to UPI (based on partially-reported internal polls). He ended up winning 61-39 over first-district congressman Dave Emery.
A better source of hope for Allen from Mitchell's political history might be his 1974 race for governor. The Press Herald gave Mitchell a 19-point lead over James B. Longley on the eve of the election, but in the end Longley pulled off a 3-point win to become the state's first independent governor.
Of course, polling has improved a bit since then.