All his rivals for the nomination believed for far too long that Trump could never be selected and therefore the last remaining alternative to Trump would inevitably become the nominee. For them the key to being selected was to remain in the race as long as their candidacy remained credible. This misjudgement meant that during the early stages of the primary campaign Trump benefitted from the persistence of a multi-candidate field. He could remain the leading candidate even though his supporters were then still only a minority of Republican voters. The longer that all but one other candidate remained in the race, the easier it was for Trump eventually to convert that minority base into a majority of Convention delegates.
Peculiarities of the candidate selection process helped Trump, but they probably would not have been enough by themselves. He was also able to exploit the fragility of the Republican Party’s electoral coalition. Until the 1970s its coalition was not as diverse as the Democrats’, and hence was usually more cohesive. It was the Democratic Party that tended to have major splits which periodically undermined its prospects in presidential elections. The re-introduction of moral issues and values into partisan politics – the Equal Rights amendment, abortion, and so on – transformed this. It was now the Republicans that had greater difficulty in keeping their broad coalition together. This becomes evident when looking at differences in the party’s success in presidential elections compared and in congressional elections. During the last 24 years the Party has controlled the White House for only one third of that period, whilst controlling both Houses of Congress for about two thirds of it. Winning the Presidency calls for unity in the national party, whereas seats in Congress can be won with idiosyncratic local strategies.
The context in which American politics is conducted has also changed massively, and this has made managing their electorates more difficult for both parties. The Democrats had to contend with vocal minority support for Bernie Sanders. Trump is just the current face of the Republican problem. Since the Republic’s birth, politics has been conducted against a background of long-term increases in the well-being of a majority of Americans. The “American Dream” remained plausible because most people could expect to be better off over their lifetimes than their parents. Economic depression – especially in the early 1890s and in the 1930s – destabilized politics, but normal politics could then resume within about a decade. Since the 1970s the real incomes of many Americans have not increased at all, even though there have been no depressions on the scale of those earlier. The benefits deriving from economic growth during the last four decades have been enjoyed primarily by the well-off. This chronic undermining of the “American Dream” is one of the factors contributing to anger among many sections of the voting population, anger that they direct towards political elites – among others. Unless there is a major redistribution of income and wealth in the future, and there is no evidence that this is occurring, then the political instability associated with the Trump candidacy might not be an isolated incident for the Republicans.
You can read the full article 'Donald Trump's Hi-jacking of the Republican Party in Historical Perspective' here.