Chris Christie: Trump campaign needs to be 'more optimistic and less dire' starting with Republican National Convention

Former New Jersey Governor and ABC News Contributor Chris Christie told the hosts of ABC News' "Powerhouse Politics" podcast on Monday that he hopes that President Donald Trump lays out an agenda at the Republican National Convention because he believes that has been the biggest failing of the Trump campaign so far.

Christie said the Trump campaign cannot run the same way they did in 2016 and he hopes that changes this week, especially Thursday night when Trump is set to give his acceptance speech.

"And so they have to do it differently this time. It has to be more optimistic and less dire. It has to be one that talks about what they want to do and how they want to leave the country at the conclusion of their eight years in," Christie told ABC News Chief White House Correspondent Jonathan Karl and Political Director Rick Klein. "I think quite frankly, that the Trump campaign has not done well on either of those fronts. And I'm hoping that's going to start to change this week, especially on Thursday night."

Since the three and a half years that Trump has been in office, Christie said that the Republican Party still stands on what they did for the last decade.

"The Republican Party still stands for much of what it stood for during a lot of the last decade or more," Christie said. "There are some things that have changed under Donald Trump for certain ... but the main Republican principles still remain pretty much the same."

Trump has said a presidency under former Vice President Joe Biden would mean "the complete and total destruction of America."

"I think what he means is that the country's going to turn into a version of the Bernie Sanders/Elizabeth Warren view of the world, which is that the government should become even larger, take over the entire health care system and take over sections of the economy that they've never had possession of before. I think that is something that Republicans, and most independents don't want to buy."

Expanding on that point, Christie said Biden -- who has referred to this as a battle for the soul of America -- "completely sold his soul to get the nomination.

"I think during their convention was to emphasize Joe Biden, the man, as a good, decent honest human being, which I found to be over the 35 years that I've known him. But he has completely sold his soul to get the nomination." Christie said. "This has become the party of Elizabeth Warren and Bernie Sanders and AOC -- and Joe Biden is merely the vessel, and certainly not the vessel they wanted, but the vessel that the Democratic primary electorate stuck with for him to pour their philosophy into."

Separately, Christie was asked about the recordings of Trump's sister that surfaced over the weekend -- in which she describes her brother as having "no principles," and alleged that "he doesn't read" and had someone take his college entrance exams on his behalf.

"I think the president and his reaction to it, Jon, is pretty much what you see is what you get," Christie said. "When he says very little like that, I'm sure this hurt him."

Christie said that he feels for the president's sister, retired U.S. Circuit Court Judge Maryanne Trump Barry, because she is being publicly embarrassed.

"The person I feel worse for this morning -- the worst for -- is Judge Barry, who I think was horribly used in the circumstance and is now being embarrassed publicly because she now has greater notoriety because her brother is the president."

As far as the general public, Christie said these recordings won't affect the decisions of voters.

"I think they know there've been problems inside the Trump family. That's been pretty well chronicled and I don't think that's going to determine anybody's vote. The people who agree with what Barry said on that tape are probably already decided not to vote for Donald Trump and vice versa. And I don't think anybody who's undecided at the moment will decide based upon these tapes."