Barnaby Joyce was probably the last politician average Australians would expect to be embroiled in a sex scandal. A comparison to Mike Pence isn’t so far-fetched: They’re both second in charge of a conservative government led by a flashy businessman, and standard-bearers for family values, tilled in the nation’s agrarian heartland. For most of the Australian public, Mr. Joyce was a bumbling farm boy who meant well.

Last week, though, a story broke that turned public sentiment against him. Following investigations by two small websites last year, the Sydney-based Daily Telegraph reported that the deputy prime minister was having a child with a former staff member, Vikki Campion. A photo on the front page of the tabloid showed Ms. Campion, pregnant and unwitting, crossing the street. (“Bundle of Joyce” said the headline.) That this story, like so many others, involves personal hypocrisy is hardly surprising. Mr. Joyce has been a strident opponent of gay marriage, basing his opposition in part on what he has called his four daughters’ right to a “secure relationship with a loving husband” and the right of every child “to know her or his mother and father.” What is more noteworthy is the degree to which the Joyce affair has sparked a long-overdue debate about the deference Australian media still accords politicians when it comes to their private lives.

Mr. Joyce’s relationship with Ms. Campion, we’ve learned in the past few days, was an open secret among the Canberra press corps. Back in October, Sharri Markson, the reporter who eventually got the print scoop, wrote a piece alluding to a “deeply personal crisis” in Mr. Joyce’s life. Now that the story’s out there, it’s very easy to read between the lines about “vicious rumors” and “personal pressures” in dozens of media clips from last year. The deputy prime minister’s private situation was well known enough that he got into a pub brawl with a constituent about it last year and apparently knocked the man’s hat off.

Did the media choose not report on Mr. Joyce because they didn’t have all the facts? Perhaps in part. As the national broadsheet The Australian has reported, repeated inquiries about Ms. Campion’s multiple job titles, let alone her taxpayer-funded salary, were met with stonewalling. Mr. Joyce would refuse to talk about the relationship when they asked. (This week, he released a statement denying that the relationship, and Ms. Campion’s employment in the government, breached ministerial rules.) Another major consideration is that Australian journalists face extremely strict libel laws, the kind Donald Trump would appreciate.