LONDON — The Brexit champion, and populist candidate for parliament, Nigel Farage, is having to apologize for the startling pro-Hitler comments of another member of his Reform UK Party. As if that weren’t enough, Mr. Farage, defeated in seven previous elections for parliament, has also been attacked by liquids hurled at him as he campaigns ahead of the pivotal snap election set for July 4. 

Best known as leader of the campaign that resulted in Britain’s exit from the European Union in 2020, Mr. Farage faces disclosures that another candidate from his Reform UK party argues Britain goofed in going to war against Nazi Germany in 1939. 

The British Broadcasting Company has dug up items posted on the message board of a British news and opinion website called UnHerd in which the candidate from another constituency, Ian Gribbin, wrote that Britain “would be in a far better state today had we taken Hitler up on his offer of neutrality.”

That thought, by itself, isn’t all that original or unusual. An historian, John Charmley, wrote a 732-page book some 30 years ago called “Churchill: The End of Glory,” taking Britain’s World War II-era prime minister to task for having plunged Britain into war. 

Mr. Gribbin, however, didn’t stop there. “Oh no,” he wrote, “Britain’s warped mindset values weird notions of international morality rather than looking after its own people.”

The Brits, he went on, “need to exorcize the cult of Churchill and recognize that in both policy and military strategy, he was abysmal.” 

Mr. Farage and Richard Tice, who turned over his post as Reform UK chairman to Mr. Farage this month, were full of apologetic explanations for Mr. Gribbin’s comments. 

The conservative prime minister, Rishi Sunak, had called the elections so suddenly,they said, they hadn’t been able to vet all the candidates of the UK Reform Party that’s challenging the Conservative Party as a leading voice against the threat of a Labor Party takeover led by Keir Starmer. 

BBC quoted Mr. Farage as saying “every party” had a problem looking into the backgrounds of its candidates while Mr. Tice promised the party would “investigate” the “inappropriate” and “daft thing” said and done by its candidates. 

Mr. Gribbin joined the chorus, according to BBC, apologizing “for these old comments,” which he said had been “taken out of context,” and withdrawing them “unreservedly.”

Mr. Farage’s campaign has inspired criticism from leftists and liberals who fear he might emerge as prime minister eventually amid a rising tide of conservatism sweeping Europe.

Lately he’s been the target of physical attacks, most recently at the town of Clackton-on-Sea, on the coast east of London, where someone in the crowd threw wet cement at him. That was a week after a woman tossed a banana milkshake at him in a rally in the same town. 

Mr. Farage is cautiously undeterred. “It’s concerning and of course it does make me thoughtful and I may need to change tactics slightly,” he said after the latest incident,” but he was sure of one thing: “I will not surrender to the mob. I will not stop campaigning. This democratic process has to continue.” 

So far Mr. Farage’s campaign is proving amazingly successful especially considering that his UK Independence Party, after achieving Brexit, faded from the political scene. His star is rising on the back of the Reform UK Party, which he founded three and a half years ago. 

One recent poll shows the party is just one percentage point behind the “ruling” Conservative Party, which commands the support of only 18 percent of the voters as opposed to 38 percent for Labor and 15 percent for Liberal Democrats, who presumably would support Labor in a showdown. 

The bottom line is that Mr. Sunak fears Reform UK would have as much influence as the opposition Labor Party in tearing down his government. The Times of London quoted him as warning that voting for candidates from Reform UK could guarantee a Labor Party leader would be in charge for “a very long time” after Mr. Starmer wins “the largest majority Labor have ever had.”