WASHINGTON • When Representative Ryan Costello of Pennsylvania announced on Sunday that he would join more than 40 other congressional Republicans not seeking re-election in November, he left no doubt about the reason: President Donald Trump's conduct made it impossible to talk about anything else.
Were he running, Mr Costello said in an interview, he would be inundated with questions about Ms Stephanie Clifford, a pornographic film actress known as Stormy Daniels, who has said she had an affair with Mr Trump and was threatened to make her stay silent about it.
"If I had a town hall (meeting) this week, it would be question after question," Mr Costello said. " 'Do you believe him or do you believe her? Why don't you believe her?' "
While Republicans have been bracing for months for a punishing election in November, they are increasingly alarmed that their losses may be even worse than feared because the midterm campaign appears destined to turn more on the behaviour of the man in the White House than any other in decades.
As much as gun control, immigration, the sweeping tax overhaul and other issues are mobilising voters on the left and the right, the seamy sex allegations and Mr Trump's erratic style could end up alienating crucial blocs of suburban voters and politically moderate women who might be drawn to some Republican policies but find the President's purported sex antics reprehensible.
Polls and every recent election show that Mr Trump has galvanised liberal and moderate voters - especially women and those with college degrees - to oppose his party. Yet, at the same time, personal loyalty to the President is increasingly the most crucial litmus test for Republicans.
This widening chasm has created a dilemma for Republicans, especially in liberal and swing states.
And perhaps most ominous for Republicans, there does not appear to be an obvious middle ground: Last November, Republican candidate Ed Gillespie sought to avoid either inflaming or embracing Mr Trump, and he was still soundly defeated.
"Trump is way more than the proverbial elephant in the room - he's the elephant in the room with political bad breath, BO and a foul mouth," said Mr Ace Smith, a veteran Democratic consultant, who argued that the last time a president's conduct loomed so large in congressional midterms was in the post-Watergate election of 1974.
Meanwhile, veteran Republican senator and forceful Trump critic John McCain is to deliver a "no-holds-barred" verdict on Mr Trump's presidency in a new book of memoirs, his publishers announced on Monday.
Although he has been undergoing treatment for brain cancer since last summer, Mr McCain has continued to voice his concerns about Mr Trump and recently questioned the nomination of a Central Intelligence Agency official once involved in torture to lead the spy agency.
NYTIMES, AGENCE FRANCE-PRESSE