The hate ****** mantra, their blatant support for speech suppression and fascism kinda changes things a bit...doesn’t it?
More to the point, since the 1970s(1968 esp.) the Democratic party has shifted more to the Hard Left such that now one needs to be fairly staunch socialist~communist to be a major contender/candidate and gain the support of the Democrat Party - DNC.
This means that on the ideological/political "pie chart", the Dems/DNC hold a narrow slice. The Libertarians hold a much smaller slice, and the assorted "other/third" parties barely a mention. Opposite the Dems/DNC is the Republican slice of that political pie, nominally those supporting free enterprise, capitalism and wealth creation are the Republicans. The Dems/DNC in contrast support larger guv'mint, more guv'mint control of industry and commerce ~ and life styles, and endorse wealth redistribution -taking from the productive and giving to the non-productive.
Between these two political poles lie about half the population, the "undecided"/"moderate"/ in-the-middle citizens/voters. Both major parts, Ds and Rs, seek to appeal to that middle half and gain their support and votes. Those whom embrace socialism/communism and seek "equity"~ equal results will flock to the Democratic Party. Those whom prefer free enterprise, true Liberty, equal rights with equal opportunity will flock to the Republican Party.
Basically, if you aren't a socialist/communist and don't support pillaging the producers of our nation, there's no place for you in the Democrat Party. Counter-point is that while the Republican Party has a political pole that is Conservative to Libertarian in main focus, the Reps/GOP is more prepared to be inclusive towards that "undecided" half in the middle. Hence the Republicans have the larger tent when measured in terms of values, standards, and goals.
In today's political climate in the USA, a person like John F. Kennedy (JFK) would not be able to be a Democrat and gain backing and support of that party. His best option would the Republican Party. Granted, some might coin him as RINO (Republican In Name Only) or CINO (Conservative In Name Only) but I personally find those terms inaccurate and distortive. If you aren't a socialist/communist there's no place for you in the Democrat Party so by default, the Republican Party accepts and embraces all and everyone whom the Democracts will reject. Hence the Republican/RNC is the real "Big Tent" of USA politics.