The Methodists have never been Calvinistic.
That is why the theology was always referred to as Wesley-Arminianism.
Some might point to George Whitfield, and I might personally be closer to George than to John, but Whitfield’s contribution to the Methodist movement died out with Whitfield.
That's not my reading of history. The Methodists were part of the Dissenters in England and many of them were definitely influenced by Calvin.
Like so much of modern religion (and maybe all religion), it may start out conservative and Scripturally-faithful, as hard as that may be, but liberalism seems to creep in without fail.
Whitefield formed and was the president of the first Methodist conference... Three churches were established in England in his name...where a form of Calvinistic Methodism similar to Whitefield's could be spread... Like his contemporary and acquaintance, Jonathan Edwards, Whitefield preached with a staunchly Calvinist theology...
George Whitefield (December 16, 1714(O.S) – September 30, 1770(N.S)) was an Anglican Protestant minister who helped spread the Great Awakening in Britain and, especially, in the British North American colonies. He was one of the founders of Methodism and of the evangelical movement generally.[1] He became perhaps the best-known preacher in Britain and America in the 18th century, and because he traveled through all of the American colonies and drew great crowds and media coverage, he was one of the most widely recognized public figures in colonial America...
And, once again, proving we learn something new every day on this forum, here's an interesting entry about what remains of those "Calvinistic Methodist churches"...
The Countess of Huntingdon's Connexion is a small society of evangelical churches, founded in 1783 by Selina, Countess of Huntingdon as a result of the Evangelical Revival. For years it was strongly associated with the Calvinist Methodist movement of George Whitefield.[1] Today, it has 23 congregations in England and some in Sierra Leone.
Whitefield's Calvinism may have nearly died out in Methodism, but we can't deny there was a Calvinistic influence in certain quarters of Methodism from the very beginning, as illustrated by Whitefield, its first president.
And today, there is a remnant.
IMO, one reason why Whitefield's influence wasn't stronger could well have been his advocacy for the legalization of slavery. While he was a benevolent owner of slaves (it was said he was revered by those who worked for him) nonetheless, it was an error both Scripturally and morally.