#LenBrown was trending on New Zealand Twitter last night and this morning, and many tweets condemned his actions.
Among calls on his Facebook page for Mr Brown to resign, Andrea Staniford said she was "absolutely appalled" and questioned his role in Ms Chuang's political aspirations.
Others supported Mr Brown, including Herald reader Nick Roughan who said: "The people of Auckland elected Len Brown to the office of mayor, not as his wife's husband. Let him answer to the electorate solely for his performance as mayor."
Deborah Pead, of Pead PR, said Mr Brown could easily recover from the scandal, but it would depend on the support of his family.
"It looks as though he is already following the right advice in that he has confessed and that is certainly the right thing to do," she said.
"The way it is handled from here on in, a lot of that depends on how his family respond to the news and how they react to it.
"If we see his wife and family coming out in support of him and they are able to forgive his transgression that will stand well for his future reputation."
Other advice Mr Brown might be receiving was to admit to any other affairs or problems, said Ms Pead.
Mr Brown should also lie low to let the dust settle and then "put his head down and deliver on being the very best mayor".
"I think if he can separate his personal and professional life, then the public will overlook this and he can move on with once again being the mayor of Auckland.
Ms Pead said the scandal did not necessarily spell the end of Mr Brown's career.
"Sex scandals are not new, in days gone by affairs used to almost be part of the leadership package - look at Clinton and Kennedy.
"In some ways - and I am not necessarily saying it is the case here - but virility almost enhances a man's leadership, it's part of the power package.
"I am reluctant to say it, but it could have been worse - he could have been caught with a prostitute."
The Department of Internal Affairs said that if a mayor stood down before he or she had been sworn in, a byelection would be held to find a new mayor.
The second-highest polling mayoral candidate did not automatically become mayor.
University of Auckland local government law expert Ken Palmer said Mr Brown had not broken any laws, and he did not believe he had breached the Auckland Council code of conduct.
Councillors could use the code to question Mr Brown and could seek a vote of censure relating to clauses addressing integrity and misuse of public property, he said.
"It's a human failing for people to have these sorts of relationships from time to time, I wouldn't have thought it's a critical thing, people go through all sorts of personal problems ...
"It seems to be relatively minor, what his alleged behaviour had been in relation to council premises, it's not as though there's $1000 spent on some private, personal ambition - that's the sort of the thing the Auditor-General would bring up, unlawful expenditure."
He did not think the scandal would hurt Mr Brown's career.
"It's a personal domestic matter and he shouldn't really suffer much of a consequence for it. I think he will recover fine."
Len Brown
1956: Born in Taumarunui, the son of a school teacher. Grew up in south Auckland, where he attended De La Salle College.
1970s: Married and split with first wife, Anne. Studied law at Auckland University.
Early 1990s: Met future wife Shan Inglis.
1992: Elected Otara Ward representative on Manukau City Council
2004: Stood for Manukau Mayoralty, but beaten by veteran Sir Barry Curtis
2007: Elected Mayor of Manukau
2008: Suffered major heart attack and had heart bypass surgery
2010: Controversy over personal spending on credit card. Cut up his credit card on TV.
October 2010: Won the first Super City mayoralty, beating rival John Banks by 50,000 votes
October 2013: Re-elected with 50,000 vote majority over nearest challenger John Pallino.
