WASHINGTON • President Donald Trump's mercurial politics is rattling Republicans heading into the 2018 mid-term campaign, sparking Trump-like primary challenges in two high-profile Senate races and a host of lower-profile House contests, while pushing a growing number of moderate House members to the exits.
Last Thursday, Representative Charlie Dent of Pennsylvania, a leader of the House Republican moderates, announced that he had had enough, following Representatives Dave Reichert of Washington and Ileana Ros-Lehtinen of Florida to a Trump-free retirement.
Trump-inspired candidates have emerged to challenge senators Dean Heller of Nevada and Jeff Flake of Arizona, two Republicans who have been targets of the President's ire, as well as House members seen as insufficiently devoted to Mr Trump, like Representative Mark Sanford of South Carolina.
And in a closely watched special Senate election in Alabama later this month, Mr Trump is waffling on his commitment to the incumbent, Mr Luther Strange, buoying the hopes of Mr Roy Moore, a former state Supreme Court justice and darling of the hard right.
"Is the House at risk? Absolutely," Mr Dent said.
Republicans fear Mr Trump has relinquished his role as party leader, instead assuming the mantle of his own political movement.
And they are bracing themselves for an election season in which their President does more to undermine than aid candidates of the party he ostensibly oversees.
Such open divisions mark an extraordinary departure from modern political tradition. Even if they feuded at times with their president, lawmakers knew they could ultimately count on the White House to endorse and raise money for incumbents, because controlling as many seats as possible would serve both their interests.
But Mr Trump's move last week to align himself with congressional Democrats over federal spending and hurricane relief cemented a view that he will not operate according to any such conventions.
Ties between Mr Trump and congressional Republicans have frayed over the lawmakers' failure to deliver on key legislation and the President's constant badgering and personal attacks against them.
But even Republicans who are uneasy about Mr Trump say lawmakers must understand the grip he holds on the conservative grassroots. "If you would go to my county Republican clubs now, they are all about Trump," said Representative Tom Rooney, Republic of Florida. "He is the party."
Sceptics, however, say Mr Trump simply does not understand that his own fate may well hinge on the success of the party's candidates.
"Hopefully, the President recognises it's in his best political interest to have as many Republicans in the Senate as possible," said Senator John Cornyn of Texas, the No. 2 Republican in the Senate, adding: "I think he can count."