The first election in which the D was left-wing and the R was right-wing

[buritobr]

I know that the polarization left-right is more applicable for European politics than it is for American politics, in which there is no strong Socialist or Social Democrat party.

But nowadays, it is possible to say that by comparing the Democratic and the Republican party, the last one is on the right in the American political spectrum and the first one is on the left.

When did it happen for the first time?

1896: Bryan X McKinley?
1916: Wilson X Hughes?
1928: Smith X Hoover?
1932: Roosevelt X Hoover?
1936: Roosevelt X Landon?

[buritobr]

Bryan was not supported by urban manufactory workers, but by poor farmers. He defended traditional values. Marx would consider him a "reactionary socialist". The electoral map of 1896 was almost the same as the map of the early 21th centrury, but the colors were switched. Even though, he opposed the candidate of the rich capitalists.
Wilson laid a basis for an welfare state, but he was less favorable to the blacks than the Republicans were.
Al Smith was not an economic interventionist, but he belonged to a religious minority and employeed women in his cabinet. Maybe, he was a predecessor of post-1980 democrats.
In 1932, Roosevelt was not a Keynesian yet. He criticized Hoover for not balancing the budget and his vice criticized Hoover for increasing the size of the public sector. But speeches in elections do not necessarily reflect the real opinion of the candidates.

Depends on different points of view if the today's party polarization started in the 1890s or in the 1930s, but one can say that since the 1930s, in every presidential election, the Republican candidate is more rightist than the Democratic candidate.

However, no earlier than 1960, the Democrats were stronger in the South than in the North. Only in 1960, Kennedy and Nixon divided the North and the South.

[buritobr]

In few words
1896 was the first time in which the Democrats were on the left and the Republicans were on the right but this aligment was reversed in some elections after that
1932 was the first election of a non-interrupted sequence of elections in which the Democrats were on the left and the Republicans were on the right

[buritobr]

So, 1896 was the first.

But, maybe, Franklin Roosevelt was more important than Willian Bryan in bringing the Democratic Party permanently to the left.

Even after Willian Bryan both the democrats and the republicans had progressive and conservative wings.

[buritobr]

How did the party of the slave owners become the party of the working class?

[buritobr]

I am pretty sure it is a myth that Republicans were Liberal.Plus hasn't the definition of the word Liberal changed in the last 200 years?

In the US: Liberal = Left-wing

Outside the US: Liberal = Right-wing, pro free-market