A Republican senator bemoaned the “cultish” atmosphere around Donald Trump the morning after allegiance to the president proved a key factor in Republican primary elections.

“It’s not a good place for any party to end up with a cult-like situation as it relates to a president that happens to be purportedly of the same party”, Bob Corker told reporters.

The Tennessee Republican occupies the increasingly lonely position of an elected Republican who is willing to publicly defy the president. Lent a freer tongue by his decision to not seek re-election, Mr Corker has sharply questioned Mr Trump’s decisions and said the administration appeared to be “just making stuff up as they go along”.

Results from the previous night’s polls demonstrated how politically perilous it can be for Republicans to oppose Mr Trump - and the potential benefits of rallying behind a president who has a potent ability to galvanise the conservative base.

In South Carolina, incumbent Republican Rep Mark Sanford lost his re-election bid to a challenger, state legislator Katie Arrington, who had savaged Mr Sanford for his habit of criticising Mr Trump and positioned herself as a loyal supporter of the president's agenda.

“We are the party of President Donald J Trump”, Ms Arrington declared after her victory.

Hours before the polls closed, Mr Trump weighed in with a tweet attacking Mr Sanford as “very unhelpful to me in my campaign to MAGA” - the acronym for Mr Trump’s campaign-trail slogan of “Make America Great Again” - and encouraged voters to rally behind Ms Arrington.

Singapore Summit: historic first meeting between Trump and Kim Jong-un Show all 20 1 /20 Singapore Summit: historic first meeting between Trump and Kim Jong-un Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim leave following their historic meeting AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim sign a document committing to peace between their nations, amongst other things EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump holds up a document that both he and Mr Kim have signed AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un The two leaders reach out to shake hands for the first time AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim shake hands as they meet for the first time Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim walk off stage, following their historic meeting Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim take a stroll after their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim interrupt their stroll to talk to the media AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim and Mr Trump look out over a balcony at the Capella hotel, where they held their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump takes questions at the press conference following his meeting with with Mr Kim AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump appreciates the crowd in the press conference following his meeting with Mr Kim Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump travels to the Istana ahead of the summit with Kim Jong Un on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Kim Jong Un travels to the Istana ahead of the summit with President Trump on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim poses for a photo with Singapore's Finance Minister Vivian Balkrishnan and Education Minister Ong Ye Kung ahead of the summit with Mr Trump Twitter/Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump shakes hands with Singapore Prime Minister Lee Hsien Loong, meeting on Monday June 11 in the Istana, Singapore's presidential palace AP Singapore Summit: historic first meeting between Trump and Kim Jong-un At a working lunch on Monday, Singapore's Prime Minister surprised Mr Trump with a birthday cake, in early celebration of his 72nd birthday later in the week EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un US Secretary of State Mike Pompeo answers questions about the summit at a press briefing in Singapore on Monday, June 11 Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un US President Donald Trump arrives at the Paya Lebar Air Base in Singapore on June 10, two days prior to his summit with North Korean leader Kim Jong Un Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim met on Tuesday June 12 in the Capella hotel on the island resort of Sentosa, just off the south coast of Singapore AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump boards Air Force One following the summit AFP/Getty

Voters in Virginia nominated a Republican senate candidate, Corey Stewart, who has enthusiastically embraced Mr Trump and is aligned with the president’s hardline approach to immigration. Mr Stewart has also embraced maintaining symbols of Confederate history, echoing Mr Trump’s complaints about removing monuments to Confederate leaders, and has associated with the architect of a deadly white supremacist rally in Charlottesville.

The president issued a tweet congratulating Mr Stewart, who had chaired Mr Trump’s campaign apparatus in Virginia, and saying he had “a major chance of winning”.

Senator Bob Corker: any senator not conflicted on Donald Trump is 'either comatose or is pretty useless in their blindness'

But other Republicans were less sanguine.National Republican Senatorial Committee chair Cory Gardner, a Colorado Republican, told reporters that the party did not plan to spend money on the Virginia Senate race, backing away from a contest in a typically competitive state.