WASHINGTON • Republican Donald Trump should fix his stumbling White House campaign in the next three weeks or step down, The Wall Street Journal said in a sharply worded warning from a leading conservative voice.
Mr Trump has alienated his party and failed to establish a competent campaign operation, the paper said in an editorial.
The Journal's editorial board, which generally favours Republicans, has been critical of Mr Trump and has questioned his conservative credentials, but its warning on Monday was its strongest attack yet.
It echoed growing alarm about Mr Trump's candidacy among many leading Republicans.
The New York real estate developer, who has never held elected office, has been mired in weeks of controversy and opinion polls show him falling behind Democratic candidate Hillary Clinton.
The Journal urged Mr Trump's backers to push the candidate to conduct himself with a more presidential demeanour and begin running a more disciplined campaign.
"If they can't get Mr Trump to change his act by Labour Day (Sept 5), the GOP will have no choice but to write off the nominee as hopeless and focus on salvaging the Senate and House and other down-ballot races," it said.
"As for Mr Trump, he needs to stop blaming everyone else and decide if he wants to behave like someone who wants to be president - or turn the nomination over to Mike Pence," it said, referring to the Indiana governor who is Mr Trump's vice-presidential running mate.
Adding to Mr Trump's woes this week was the news that the name of his campaign manager, Mr Paul Manafort, was in secret ledgers showing cash payments designated to him of more than US$12 million (S$16 million) from a Ukrainian political party with close ties to Russia.
Mr Manafort denied any impropriety in a statement on Monday.