WASHINGTON — President Trump’s mercurial politics are already rattling Republicans heading into the 2018 midterm 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.
On Thursday night, 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, such as 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, Senator Luther Strange, buoying the hopes of Roy Moore, a former State Supreme Court justice and darling of the hard right.
Republicans fear that Mr. Trump has relinquished his role as leader of the party, instead assuming the mantle of his own political movement. And they are bracing for an election season in which their deeply unpopular president does more to undermine than aid candidates of the party he ostensibly oversees.
“It’s a cult of personality,” said Mr. Sanford, who faces a primary challenge from a state legislator who charges that the congressman has been inadequately loyal to the president. “He’s fundamentally, at the core, about Donald Trump. He’s not about ideas. And ideas are what parties are supposedly based on.”
Such open divisions between a president and elected officials of the same party 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 decision to align himself with congressional Democrats this week over federal spending and hurricane relief cemented a view that he will not operate according to any such conventions. Relations between the president and congressional Republicans have frayed over the lawmakers’ failure to deliver on key legislation and Mr. Trump’s constant badgering and personal attacks against them.