"Never pick a fight with people who buy ink by the barrel," advised the writer Mark Twain.
Once, politicians lived by these words. In Australia, it meant you didn't pick a fight with Rupert Murdoch and News Corp, which accounts for 60 per cent of daily newspaper sales.
But this week Labor leader Bill Shorten abandoned the American novellist's directive and took on the Murdoch press.
Following tough coverage of Labor's plan to cap deductions for managing tax affairs, Shorten hit out at the "dishonest scare campaigns" and "usual propaganda from News Corp".
And facing growing scrutiny over the economic cost of driving down greenhouse gas emissions, the Opposition Leader lashed the "News Corp climate change deniers and of course their ally, the Prime Minister".
The public attacks follow his declaration that he has no intention of meeting with Murdoch personally, breaking with the practice of past Labor leaders.
The reasons for Labor's increased public hostility towards News Corp reflect both long-held truths about politics and the realities of the modern media landscape. They also vary depending on who you ask.
"It's just become fairly apparent that they are acting as a propaganda arm of the government," says one senior Labor source. "We know that they are going to do everything they can to help the other side stay in power."
Another party operative says some MPs and political staffers have "had a gutful" of particular newspapers and cable news channel Sky News, which has become a hub of conservative commentary since News Corp took full control in late 2016.
One News Corp employee observes that Shorten is the first Labor leader to seek the prime ministership without working hard to keep Murdoch on side. Former leaders Kevin Rudd and Julia Gillard sought to woo the billionaire before relations soured in government.
Today, party strategists are confident they can get away with thumbing their noses at publications suffering from declining circulation and relevance. Social media offers politicians a way of bypassing the filter and accountability of traditional media outlets.
"With the rise of digital channels, you have other means of getting a message through to supporters and people you're seeking to persuade," one Labor source says.
The party also regards Murdoch's platforms as less important for its side of politics, compared to the Coalition which sees them as a key way of speaking to a conservative voting base.
One paper attracting particular ire is Sydney's Daily Telegraph. Recent front pages have warned of Labor's "tax time bomb" and called the party's electric vehicle policy "Bill's $5k car-bon tax".
Another target is Brisbane's Courier Mail. The front page of its federal budget edition depicted a road sign promising "REWARD" if the Coalition was re-elected and "RISK" with Labor.
It was in Brisbane that Shorten addressed a gathering of News Corp editors earlier this year. The meeting was said to be cordial with perhaps a hint of irritation from Shorten about some of the treatment of his party.
One person who was present says the Labor leader was relaxed, enjoyed the interactions and has stronger relationships with News Corp figures than his public comments suggest.
"It obviously plays better for those on his left for him to demonise News and be publicly at war with our papers," says a company insider.
It is well-known that Labor and Shorten generally enjoy a better relationship with the Herald Sun in Melbourne than some other mastheads in the Murdoch stable.
Ben English, the editor of the Daily Telegaph, says it's business-as-usual and rejects the idea there has been a conscious hardening of coverage.
"It's certainly not a considered strategy on our behalf to become more polemical or more strident one way or the other," he says. "That's not really what drives us. What drives us is to cover the stories and the issues that matter to readers."
English sees Shorten's comments as a run-of-the-mill political tactic as the pressure of the election campaign grows.
Chris Dore, the editor-in-chief of The Australian, says Shorten should be straightforward about the cost of Labor's climate change policy instead of attacking the media.
"It's a curious tactic one week into the campaign to question the motives of an inquisitive media who are simply asking questions and examining policies that will have a deep and lasting impact on our readers," he says.
But some media and political observers say there is growing polarisation of the news and opinion environment, with outlets increasingly catering to a core audience that craves validation of their pre-existing views.
Chris Mitchell, a former editor-in-chief of The Australian, argues this has been happening globally, including in the United States where President Donald Trump has made a sport of bashing outlets that publish unfavourable stories.
"I think that what's happened in the digital age is people are identifying with newspapers that reflect their political position," he says. "You have seen this increase in partisanship in the old media."
In a world ruled by social media algorithms and internet traffic, Twain's advice is no longer gospel.