Donald Trump was once seen as being a little too cozy with "Morning Joe" hosts Joe Scarborough and Mika Brzezinski. The Fix's Callum Borchers explains how the relationship went downhill. (Peter Stevenson/The Washington Post)

Donald Trump escalated his feud with the hosts of MSNBC's "Morning Joe" Monday, repeating a rumor straight off Page Six that Joe Scarborough and Mika Brzezinski are romantically involved.

The New York Post's popular gossip page speculated in June that Scarborough and Brzezinski "could soon go public as a couple" following Brzezinski's divorce from her husband of 23 years. Scarborough and his wife divorced in 2013. Page Six's Emily Smith quoted an "NBC insider" who claimed "everybody at 30 Rock knows they are a couple."

This is hardly Trump's first foray into tabloid-style rumor and innuendo. In May, he linked Ted Cruz's father to John F. Kennedy's assassin, based on a story in the National Enquirer, which he said "should be very respected." He previously tweeted a vague threat to "spill the beans" about the Texas senator's wife, Heidi, and last month tweeted a cryptic message in which he claimed to "know more about [Sen.] Cory [Booker (D-N.J.)] than he knows about himself." Leading theories are that the Republican presidential nominee was suggesting Booker is gay and referring to Heidi Cruz's battle against depression.

No need to guess what Trump was talking about this time.

It is also no surprise that Trump would engage in Page Six gossip (which has circulated elsewhere, too), given that his list of go-to news sources includes the National Enquirer, Infowars and World Net Daily.

Anyway, Trump did not stop his "Morning Joe" attack at a single tweet. Neither did Scarborough, a contributor to The Washington Post opinion section, who responded.

http://twitter.com/JoeNBC/status/767696649309347841

The back-and-forth illustrates once again just how badly the relationship between Trump and "Morning Joe" has deteriorated over the course of the election. Six months ago, in the early stages of the Republican primary, Scarborough and Brzezinski were widely viewed as being too cozy with the business executive, who was a frequent guest on their show. The co-hosts were quick to take Trump's candidacy seriously — last year, Brzezinski bet colleague Mike Barnicle that Trump would win the Republican nomination — and the billionaire even thanked the duo for being "supporters" after winning the New Hampshire primary in February.

Scarborough and Brzezinski always maintained they were not supporters but merely believers in Trump's political prospects. When Scarborough said on the air in May that he could never vote for Trump, the dynamic changed dramatically.

Despite saying he "won't do or watch the show anymore," Trump did appear on "Morning Joe" in May. The interview was awkward, with neither side acknowledging any tension. Brzezinski's wrap-up summarized things perfectly: "Donald Trump, thank you so much for joining us — I think."

By June, the fight was raging again.

Ratings represent a common thread throughout Trump's broadsides, but he took things to a new, more personal level Monday by amplifying the dating rumor. "Morning Joe" will be worth watching this week to see if the hosts respond in kind. Recall that earlier this month, Scarborough shared a conversation he said he had with a "foreign policy expert" who claimed Trump asked multiple times during a briefing session why the United States can't use nuclear weapons. Scarborough later told the New York Times's Jim Rutenberg that he hadn't planned to mention the conversation on the air but did so on impulse because "that was something I thought Americans needed to know."

It appears both parties are now willing to talk publicly about things they have been keeping private.