In the 1920s, the Republican Party was dominant and worked to undermine immigration to the United States, which had reached record levels from 1880-1920, bringing into America millions of immigrants of Catholic and Jewish origin, as well as smaller numbers from Asia, particularly Japan.
In the early 1920s, under Warren G. Harding and Calvin Coolidge, stringent immigration laws were put into place, cutting down the so called “new” immigration of these groups, who mostly had settled in the major urban centers, and become Democratic strongholds.
The growth of these Democratic strongholds in the cities helped to bring about a Democratic majority during the Great Depression, and led to the rise of the Democratic Party as the majority party, with the Republicans seen as the party of white Anglo Saxon Protestants.
While in future generations, the Republicans would gain a percentage of about one third to 40 percent of the Jewish and Catholic vote, they never were able to appeal to these groups and gain a majority, due to their clear cut nativism. This was a major blunder on their part, which undermined their ability to become the majority party that they had once been from the Civil War to the Great Depression.
Now in recent years, the new nativism has occurred, as the Republicans promote and advocate anti Hispanic and anti Asian propaganda, and therefore, those groups overwhelmingly support the Democrats, along with African Americans, who realize that while some Republicans supported the Civil Rights Acts in the 1960s, no longer do Republicans concern themselves with the plight of African Americans.
So the new nativism is in play, and the Republicans cannot win the White House, and will have trouble retaining control of the US Senate, as long as they spew forth nativist propaganda.
The Republican Party knows they are in a bind, but with Donald Trump using anti Hispanic propaganda, and other candidates showing insensitivity toward legal immigrants and undocumented immigrants, they are definitely doomed to fail, and lose the White House for the long term, with the growing number of people of Hispanic and Asian ancestry, who are not about to vote for the party that trashes them.
Once Texas turns “Blue”, and Georgia and North Carolina eventually, and with Virginia and Florida becoming more reliably “Blue” in Presidential elections, the Electoral College will favor the Democrats. The Republican Party, if it survives in is present form, will be doomed for many decades to be unable to win the Presidency!