Both Donald Trump and Boris Johnson share an "elastic relationship with the truth", the former chairman of the Conservative Party has said.
Lord Patten also accused Mr Johnson or his senior adviser Dominic Cummings of turning the Conservative Party into a "rather narrow sectarian English nationalist party".
He added that he could think of some "serial mutton-heads" who could be leader of the Conservative Party, and would stand a good chance of beating "hopeless" Jeremy Corbyn.
Speaking on BBC Radio 5 Live's Emma Barnett Show, Lord Patten said: "I think they (President Trump and Mr Johnson) share some of the same characteristics. I think both of them have a certain, rather elastic relationship with the truth. I think that, for them, the issue is not governing, it's campaigning.
"Mr Trump is campaigning the whole time and I think Boris campaigns most of the time without thinking about what the consequences of what he says may be.
"I think it's a terrible shame that when the British Prime Minister talks about trust and being trusted, BBC and other audiences laugh out loud in his face, and Mr Johnson doesn't seem to be worried by that.
"I think it's pretty awful and very sad for our democracy."
Accusing Mr Johnson or Mr Cummings of turning the Tory Party into a "narrow sectarian English nationalist party", he added: "I think that's grist to Mr Trump's mill. I think he likes seeing nationalists and he's prepared to support anybody who is a nationalist, even people like Mr Erdogan."
Lord Patten said that he believes this election campaign has been overshadowed by "spectacular delusions".
He added: "There's always a degree of spin that goes on, and not everything that's said is entirely truthful.
"But I think this campaign has been marked by spectacular delusions and spectacular examples of mendacity along the way, right from Get Brexit Done in the first place, the arguments for holding the election that were spurious, the fact that even the Queen was involved I think in a dishonourable way in the attempt to set up the election - I think all that is very bad for us.
"We did have a sense of good guys on both sides who knew how far to go, knew there were some lines that they shouldn't cross, and I think we've lost that for the time being, and I think it's really sad."
Quoting former US secretary of state Henry Kissinger, Lord Patten added that "it's a pity both sides can't lose" the upcoming election.
"There can't be any circumstances more propitious for any Conservative to win an election.
"I could think of some serial mutton-heads who could be leader of the Conservative Party, and would stand a very good chance of beating Mr Corbyn.
"I don't think he's a bad person, I just think he's hopeless. The Venezuelan economics that he's offering people would I think be a real disaster," he said.
The peer added: "The thing you can't do in our electoral system unfortunately, the thing you can't do, is vote for a hung Parliament."
Lord Patten - who cannot vote as a member of the House of Lords - indicated that, if he had a vote, he would find it hard to vote Conservative.
He said: "I couldn't vote for any candidate who had voted in the past for a no-deal Brexit. Nor could I vote for a candidate who wouldn't make it clear that in the future he or she wouldn't vote for a no-deal Brexit.
"Now I'm sure there are some Conservatives who feel quite strongly that they wouldn't accept a no-deal Brexit, in which case I could support them.
"Otherwise I would be looking on the ballot paper for who would be sensible about Brexit over the next months and years, and who also represented integrity and principle across the board."
Lord Patten added that he does not believe a "huge trade deal" can be done with the US.
"No, I don't think we can. We may be able to do some side deals but it won't be something which is better than the market which we've got in Europe at the moment," he said.