The war between Donald Trump and CNN has taken a new turn with the government's challenge to a tie-up between AT&T and the cable news channel's parent firm Time Warner.

Even as his Justice Department moved to block the deal, the president has stepped up his attacks on the major news network, his most frequent target of ‘fake news’ complaints.

Trump has been attacking CNN since the 2016 campaign, but the latest developments raise questions about whether he is using his power to choke off investment, or even force CNN to be sold to a partner friendlier to the White House.

As the atmosphere has deteriorated, CNN said it would boycott the White House Christmas party ‘in light of the president's continued attacks on freedom of the press and CNN.’

Trump returned the compliment, with a tweet saying, ‘Great, and we should boycott Fake News CNN. Dealing with them is a total waste of time!’

CNN is not the dominant force in television news it was decades ago, as Fox News has attracted conservative viewers and MSNBC from the left.

‘Unfortunately, our polarized political climate is being reflected in the high ratings for partisan cable outlets,’ said Dannagal Young, a University of Delaware professor of communications.

‘However, from a democratic perspective, the viability of CNN is arguably more important than ever.’

- Vindictiveness? -

The massive buyout of Time Warner by AT&T is now in court, with the companies claiming that because it is a ‘vertical’ merger with no overlap of services, competition would not be impacted.

AT&T has said it has no indication that Trump is behind the effort to block the deal.

But some analysts say it's difficult to separate the legal questions from the political feud between Trump and CNN.

Gabriel Kahn, a journalism professor at the University of Southern California's Annenberg School, called the antitrust action ‘highly suspect.’

‘Trump's public war with the network, the fact that he repeatedly demonstrates a vindictiveness against those whom he feels have slighted him, and the way he has politicized every decision in his administration gives good reason to make this quite suspicious,’ Kahn said.

‘In addition, there is no monopoly on news. Not even close. The market share of even major news organizations has never been slimmer. The sector is gurgling with competition. And AT&T has no real news presence either.’

Trump has gone so far as to launch personal attacks on a CNN journalist during a news conference, and to retweet a video clip in which he appears to slam a CNN avatar to the ground.

CNN, launched by Ted Turner as part of his cable empire, was the only all-news channel from 1980 to 1996, and gained prominence for its coverage of the 1991 Gulf War.

- It's all theater -

Part of Time Warner since 1996, CNN helped lay the groundwork for modern television journalism with its ‘breaking news,’ its live debates and making news part of the entertainment cycle. It also has a strong international presence.

CNN has been overtaken in viewership by its rivals, failing to benefit from the polarized political atmosphere in the Trump era.

CNN president Jeff Zucker said the mission of the organization remains unchanged.

‘We are about the facts. We are about the truth... I don't think the core mission has changed at all in 37 years,’ he said in October. ‘We have tried to hold those in power accountable.’

Young said the tone of CNN is ‘middle-of-the-road ideologically, but pointedly critical of the Trump presidency, in particular the way in which the presidency violates core democratic norms.’

According to Kahn, ‘Fox News serves the right and MSNBC serves the left. This left CNN without a mission for a long time. But now it's the place to see the two sides yell at one another.’

Kahn said that whether or not the antitrust action is politically motivated, it does appear to help the president.

‘I think anything that appears to punish CNN plays well with Trump's base,’ he said. ‘Everything has been reduced to theater.’