I know my friend's politics quite well. His ideal candidate would merge the ideological purity of Bernie Sanders with Barack Obama's pragmatism; at the other extreme would be Ted Cruz. Rather than his "voting life", while I can guess the date range of that, I will go for a larger sample, all of his life. He's just coming up on his 60th birthday, so I will range from 1956 forward, but judging the candidates by the political standards of their times, not our current era's. The other stipulation is that I will consider only the major party nominees.
Counting this year's presumptive nominees, there are 24 different major-party candidates in those 16 elections. Richard Nixon is the only three-time candidate (two wins, one loss). Six ran twice in the chosen time frame; there are no two-time losers (because Adlai Stevenson's first loss was before, in 1952), and there are only two among them who won once and lost once (Jimmy Carter and Poppy Bush). The other 17 ran only once, and a whole bunch of them never got to demonstrate their policies' theoretical appeal while governing in the White House. Here is my ranking of them on the policy dimension, from "most appealing" to least.
George McGovern (1972); Stevenson (1956); Dukakis (1980); Hubert Humphrey (1968); John Kerry (2004); Obama (2008-12); Al Gore (2000); Walter Mondale (1984); Jimmy Carter (1976-80); Lyndon Johnson (1964); John Kennedy (1960); WJ Clinton (1992-96); DD Eisenhower (1956); GHW Bush (1988-92); Nixon (1960, 1968-72), Gerald Ford (1976); Mitt Romney (2012); Bob Dole (1996); John McCain (2008); Barry Goldwater (2004); Ronald Reagan (1980-84); and George W. Bush (2000-04).
Where to place the current ones on the policy appeal spectrum for my liberal friend? I would put Hillary just after Eisenhower, and Donald Trump just above Goldwater. There are some certainly some close calls in there, but I feel good about the ranking in general.
But wait, there's more. The overall appeal of a candidate should be based not just on the policy positions he (or, now, she) holds, but also on that candidate's potential to head a winning campaign. A positive but weak candidate offers little promise to the potential voter; similarly, a negative, strong candidate poses greater danger than a negative one who can't get elected. In fact, knowing my friend, his comment denigrating Hillary must be based at least as much on her weakness as an electoral draw (in his view) as with dissatisfaction with her policies. (Though it could be just personal distaste, but I will give him more credit than that.)
So, my ranking on potential or demonstrated competency in heading a general election campaign is as follows (best to worst):
Reagan; Obama; WJClinton; Eisenhower; Johnson; Kennedy; GW Bush; Nixon; Carter; Trump; Romney; McCain; Gore; Humphrey; GHW Bush; Kerry; HR Clinton; Ford; Stevenson; Dole; Dukakis; Stevenson; McGovern; Mondale.
That ranking is largely based on the track record (wins and losses), but secondarily on the quality of the opponent(s), with tiebreakers based on my observations on their skills, or lack of skills, in things like debates, organizing a campaign team, building a coalition, sticking to an effective script, improvising, etc. I rate Trump (#10 of the 24) higher than Hillary (#17) by quite a bit, because of his mastery of public relations (and her lack of it) and psychological warfare, and I don't give Hillary much credit for being a highly competent, but unexciting, debater. Of course their mettle has not yet been put to the definitive test. If Hillary wins from this position, she would be the lowest-rated campaigner to win a general election in his lifetime.
I now put these two sets of rankings together to make a composite measure of the "Benefit/Damage Capacity"; again, from my friend's point of view. The approach I have chosen is to look at the variation from the mean ranking (12.5), in terms of the policy ranking; then adjusting by the variation from the mean on electability: those positive on policy gain benefit by being more electable (and lose it by being unelectable); while the negative value for those worse than average is intensified if they are more electable.
The table below gives the results:
The majority of the candidates clearly fall into the “meh” category; either moderate, not very electable, or both. Most of the ones who are ideologically potent, either positive or negative (always from the point of view ascribed to “my friend”), make up for it by watering down their potency with weak electoral skills. The ones at the extreme ends of this composite ranking—Obama, Slick Willie Clinton, Reagan, Dubya--were either unusually strong moderates, or the potent combination of hardcore conservative with folksy appeal.
There is one other exception to the variety of meh-ness, and his case frankly shows the weakness of this approach. On the policy scale, I would argue that Eisenhower was moderately appealing, he should probably be the highest-rated Republican from my liberal friend’s perspective of all candidates in his lifetime. (Nixon did have some progressive accomplishments to his name, but we know better: they were sops to the left at a time his team was at its weakest in Congress, and he didn’t really mean it.) Ike was a “progressive conservative” in some meaningful senses: he opposed segregation in Little Rock, built infrastructure, appointed liberal Supreme Court justices Earl Warren and Potter Stewart, and wisely gave his greatest attention to those things that modern American Presidents do which really matter: foreign and military affairs. In a very conservative time, he dared to pick some spots to challenge the sleepy Cold War consensus (think of his historically significant comment referring to the "military-industrial complex").
Here’s the point: he’s right in the middle on the “policy appeal” scale; I put him slightly below the median. His slightly negative value on policy appeal becomes magnified by his enormous electability to make him one of the greater negative-value candidates of the era. This is unfair to him: if you move him up one slot, to twelfth, his value becomes positive vs. the mean and he goes up to the top rank on the positive side.
Hillary drops right in there around Bill and Ike; in her spot (again, slightly negative), her low electability makes her a net positive (her slightly negative appeal is more than canceled by the “positive” of being low in potential). If, though, we shift her up two slots, to twelfth, she becomes a net negative (-4 to be precise). Either way, though, she fits into that mediocre group and is nowhere near the worst.
As for Trump, I would argue that ideologically he is not the most diametrically opposite candidate to our ideal, though he has aspects within his limited range of expressed policy positions that are unusually toxic. On social issues, or on tendency toward military aggression, he was nowhere near the worst in his party's field this year. (Though, speaking of "least appealing POTUS candidate", there were about 15 worse than Hillary running this year.) Neither is he one of the strongest candidates from the point of view of electability, but I see him as clearly ranking third-worst in terms of damage potential. Of course, I may be underrating him—it’s happened before.