Lots of good points already made.
- His knee infection kept him off the news early on while Kennedy became the media darling.
- He declined to use Ike extensively, deciding it was improper to risk the President's health with extensive campaining. I did, however, see Ike make an appearance at a huge rally in Nassau Co, NY in mid-Oct 1960. Rockefeller and Lodge were also there.
- His pledge to campaign in all 50 states was timed poorly. Being in Alaska as the campaign ended while Kennedy had huge rallies in eastern states was just plain dumb. Never would happen today. And his knee infection likely delayed the Alaska trip to the very end.
- His choice of Lodge probably hurt more than helped. No way were they going to carry Massachusetts. Perhaps Sen Clifford Case of NJ would have swung that state to Nixon.
Making up 50 EVs hard to do? In this election not at all!
http://members.cox.net/rbt48/weather/Presidential_Elections/1960%20election%20spreadsheet.pdf Toss in IL (change 5,000 votes) for 27 EVs, MO (chage another 5,000 votes) for 13 EVs, and NJ (change another 12,000 votes) for 16 EVs and you are there. Or skip NJ and MO and, instead, change 24,000 votes in TX for another 24 EVs and you get Nixon to 270. So for a change of less than 22,000 popular votes and Nixon wins the election.