Ronald Reagan’s Republican party is often said to have stood on three ideological pillars: social conservatism, economic conservatism, and muscular internationalism. Running for elections in 2007, Mitt Romney acknowledged this “three-legged stool”, saying that if any one of those legs was to be chopped off, the stool would crash to the ground.

But take a look at Donald Trump’s frontrunning campaign and you could be excused for thinking that he’s competing in a very different party. Trump was never supposed to be a mainstream Republican and his run-ins with the party’s elites are fairly well known.

Take social conservatism, on which Donald Trump has vacillated. Early this year, Trump promised that he would overturn the legalization of same-sex marriage. But in 2005, Trump wrote a blog post celebrating Elton John’s marriage with his longtime partner David Furnish. Then, in a bid to woo evangelical voters, Trump tried to play up his Christian credentials, but that followed an ugly tiff with Pope Francis.

Trump’s indecision on social conservatism is in many ways symptomatic of the growing divisions within his party. In a 2014 Pew Survey, 45 percent of Republican respondents said that they were unhappy with their party’s stand on abortion and gay marriage – both cornerstones of conservative belief.

On economic conservatism too, Trump has thrown up divisions among the Republicans. Trump has often called for a reversal of free trade Republicanism, in favor of economic patriotism, telling enthusiastic voters that America often gets the short end of the stick on international deals.

Then there’s his opposition to the traditionally internationalist foreign policy long espoused by Republicans. Even as party elites have called for greater American involvement in matters of international security, in the face of growing threat from groups such as the Islamic State (ISIS), Trump has advocated a more isolationist foreign policy, criticizing former President George W Bush for his interventions in Iraq and Afghanistan.

Trump has often voiced his disapproval of America’s long-standing mutual defence alliances with countries around the world, arguing that Washington does far too much of the heavy lifting – all proposals which fly in the face of traditional Republican foreign policy.

Trump’s popularity among Republican voters (he now has nearly as many pledged delegates as Ted Cruz and Marco Rubio put together) has therefore understandably alarmed traditional Republican ideologues. But it also signifies rifts within the Republican party, dissatisfaction among Republican voters, and an internal rebellion that threatens to change the face of the Republican party altogether.