Starting since Nixon there have been six Republican Presidents. Of those six, three, fully half of them have comported with a nominal enemy of the United States to create circumstances that made the odds of their winning the Presidency go up. No Democratic President has been accused of that in any credible way.
Nixon: Worked with the Chinese and North Vietnam to kill the peace talks between North and South Vietnam. This came out recently due to declassification dates being passed.
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Ford: Free and clear no comporting with the enemies of the United States
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Reagan: Negotiated with Iran to time the release of American Hostages in Iran until after his election and also to make Carter look incompetent and weak. This was part of Iran Contra. They traded arms to Iran in exchange for this cooperation. This is still slightly up in the air.
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George H. W. Bush: Free and clear although he was implicated to a degree in the Iran Contra controversy.
George W. Bush: Free and clear but his Vice President was very likely involved in outing a CIA undercover agent, Valerie Plame via one of his underlings, Scooter Libby.
We finally come to Trump. Likely but still to be proved conspired with Russia to influence and interfere in the US Election in 2016. Definitely a fair number of his election and administration staff have been implicated and are slowing being brought to Justice. Even if not he is not working with the enemies of the United States he is doing unconstitutional and illegal acts.
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