MR Johnson ruled out an election pact with Nigel Farage to stop his Brexit Party destroying the Tories.
The frontrunner said there will be no need to do a deal if he leads Britain out of the EU on time – and comes up with a “great programme” for the future.
He added: “Everyone should be very, very optimistic about our agenda.
“People say why don’t you do a deal with this or that other party? I see no point in that. We’ve got to believe in our own party.
“As Nigel Farage will tell you, there was a historic meeting 25 years or so ago in a pub when he tried to recruit me and I tried to recruit him. It didn’t get anywhere and we went our separate ways.
“We are going to deliver Brexit and that’s what I hope Sun on Sunday readers will recognise. We’re the only party that can keep out Jeremy Corbyn – all the Brexit Party or Lib Dems can do is let him in.”
The hot favourite for the Tory leadership admitted he will make a “different sort” of PM — avoiding a repeat of Theresa May’s cautious approach for a more swashbuckling style.
In an interview with The Sun on Sunday, he insisted he will be batting for Britain with “maximum energy” and fighting to win.
Mr Johnson said: “For the last three years, quite frankly, we’ve had nothing but a diet of miserabilism. We can’t do this, we can’t do that. You know, ‘Computer says no’. And it’s really wretched.
“I think probably I’m going to be a different sort of Prime Minister in the sense that throughout my political career, I’ve tended to go for my shots.
“Sometimes I get out and sometimes I hit some runs. So let’s knock it out of the park. Well, I think, at least have a go.”