It was perhaps the worst insult South Carolina's hawkish senator, Lindsey Graham, could have directed at a fellow Republican. On the day his Senate colleague, Rand Paul, officially announced last week he was running for President, Mr Graham declared him to be "in many ways to the left of Barack Obama".

But Mr Graham, who is himself mulling a bid for the Republican presidential nomination, was hardly a lone wolf savaging Kentucky's libertarian senator. Despite getting a lift from polls, which show him to be the strongest Republican candidate, Mr Paul has come under some distinctly unfriendly fire from elements of the American right.

The Foundation for a Safe and Prosperous America, led by the strategist behind the Swiftboat Veterans for Truth campaign which sunk John Kerry's attempt to deny George W Bush re-election in 2004, began airing ads – complete with mushroom clouds – in early primary states accusing Mr Paul of being soft on Iran.

It is, however, his stance on Israel, not Iran, which is exhibit one in building the case that Mr Paul is "closest to Obama in his view of foreign policy", as conservative columnist Charles Krauthammer suggested last week. Shortly after entering the Senate in 2011, Mr Paul proposed a budget which eliminated all foreign aid, including to Israel. Asked to defend his position at the time, the senator was unequivocal: "Should we be giving free money or welfare to a wealthy nation? I don't think so." He later questioned whether it was wise to fund "both sides of an arms race". Two years later, on a visit to Jerusalem, he reiterated his position: the US couldn't be a good friend to Israel if it went broke, he argued.

In the wake of the rise of Islamic State, the isolationism that Mr Paul once encapsulated no longer has the popular appeal it did just a year ago.

And it is on Israel that the Kentucky senator's handbrake turn is most evident. Aside from donning a yarmulke, praying at the Western Wall and visiting a New Jersey yeshivah, Mr Paul has been touting his proposed "Stand With Israel Act", which eliminates aid to the Palestinian Authority until it cuts ties with Hamas, and his support – last summer – for increased funding for Iron Dome. All this as he assiduously courts the influential Republican Jewish Coalition.

As Democrats and fellow Republicans gleefully reminded the media of his previous positions, Mr Paul unsuccessfully attempted to fend off suggestions that he'd committed that most cardinal of sins in American politics: the flip-flop. Against all evidence to the contrary, he testily insisted in interviews that he'd never proposed cutting off aid to Israel – thus appearing to hope, noted one journalist disdainfully, that "we've all lost the ability to use search engines".