The more charismatic candidate always wins

[Senator Spark]

How true is this?

True in each of the last 15 Presidential elections, going back to 1960, with the possible exceptions of 1968 and 1972.
1960- Kennedy's charisma was legendary.
1964- Johnson was folksy; Goldwater may have come across as stern sometimes.
1968- Probably a 3-way tie in terms of charisma. Humphrey, ever eager to please; Nixon, statesmanlike in demeanor.
1972- McGovern (I have heard) was a rather boring speaker; though Nixon was a bit of a grouch.
1976- Carter again was folksy and down-home; Ford was a bit more awkward.
1980- Reagan was the Great Communicator.
1984- Ditto ("I will not make age an issue of this campaign. I will not exploit, for political purposes, my opponent's youth and inexperience").
1988- Bush performed better than expected. "Read my lips"
1992- Clinton had charisma.
1996- Ditto
2000- Bush seemed folksy; Gore seemed wooden and automaton-iike.
2004- Bush, still folksy.
2008- Obama had charisma.
2012- Obama had charisma.
2016- I guess you could call Trump's campaign style a form of charisma, but Hillary Clinton certainly did not have the political savvy of her husband.