The tweets came after several big-name Republicans announced they could no longer support their presidential nominee in the wake of the publication of a 2005 video showing Trump bragging about groping women. Trump apologized for what he called "locker room talk."
On Monday, Ryan said he would no longer defend Trump through the last month of the general election — but he stopped short of rescinding his endorsement of the New York businessman.
In the morning messages, Trump said "the shackles" had been removed and "disloyal" members of his own party are more of an impediment than Hillary Clinton. And in an afternoon tweet, the GOP nominee attacked Sen. John McCain of Arizona — who said Saturday that he would not vote for Trump.
Trump tweet 1: Despite winning the second debate in a landslide (every poll), it is hard to do well when Paul Ryan and others give zero support!
Trump tweet 2: Our very weak and ineffective leader, Paul Ryan, had a bad conference call where his members went wild at his disloyalty.
Trump tweet 3: It is so nice that the shackles have been taken off me and I can now fight for America the way I want to.
Trump tweet 4: With the exception of cheating Bernie out of the nom the Dems have always proven to be far more loyal to each other than the Republicans!
Trump tweet 5: Disloyal R's are far more difficult than Crooked Hillary. They come at you from all sides. They don't know how to win - I will teach them!
Trump tweet 6: The very foul mouthed Sen. John McCain begged for my support during his primary (I gave, he won), then dropped me over locker room remarks!
Pundits have warned for some time that the Republican Party could be on the verge of a civil war.
Former House Speaker Newt Gingrich told CNBC on Monday that a "historic" break in the party could be brewing. A Trump supporter, Gingrich said those who are hoping to "manage decay" under a Clinton White House risk a long-term split with elements of the Republican grassroots.
A spokesman for the House speaker said, "Paul Ryan is focusing the next month on defeating Democrats, and all Republicans running for office should probably do the same."
As Trump attacked the speaker's fidelity, Ryan's own Twitter account posted a series of policy discussions on Tuesday morning but nothing about Trump.
During the primary season, Trump rose to prominence by attacking the "establishment" elements of his party, whom he painted as self-serving and unconcerned with the general populace's well-being. That populist tactic had seen less use, however, during the general election as Trump sought to win over moderate voters.
Ryan endorsed Trump in June — weeks after the businessman had become the presumptive nominee.
—CNBC's John Harwood contributed to this report.
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