We don't. The primaries are extragovernmental affairs controlled by private entities, the two main political parties. If you wish to change the process, you must become involved in party politics at a national level, and have a monumental amount of influence within that organization.
James
From the groundbreaking 2014 Princeton University study which got virtually no mass media attention here in the U.S.:
Testing Theories of American Politics: Elites, Interest Groups, and Average Citizens
https://scholar.princeton.edu/sites...testing_theories_of_american_politics.doc.pdf
Excerpts:
A great deal of empirical research speaks to the policy influence of one or another set of actors, but until recently it has not been possible to test these contrasting theoretical predictions against each other within a single statistical model. We report on an effort to do so, using a unique data set that includes measures of the key variables for 1,779 policy issues.
Multivariate analysis indicates that economic elites and organized groups representing business interests have substantial independent impacts on U.S. government policy, while average citizens and mass-based interest groups have little or no independent influence. The results provide substantial support for theories of Economic-Elite Domination and for theories of Biased Pluralism, but not for theories of Majoritarian Electoral Democracy or Majoritarian Pluralism.
In the United States, our findings indicate, the majority does not rule—at least not in the causal sense of actually determining policy outcomes. When a majority of citizens disagrees with economic elites or with organized interests, they generally lose. Moreover, because of the strong status quo bias built into the U.S. political system, even when fairly large majorities of Americans favor policy change, they generally do not get it.
...the preferences of economic elites (as measured by our proxy, the preferences of “affluent” citizens) have far more independent impact upon policy change than the preferences of average citizens do. To be sure, this does not mean that ordinary citizens always lose out; they fairly often get the policies they favor, but only because those policies happen also to be preferred by the economically-elite citizens who wield the actual influence.
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“Now [the United States is] just an oligarchy, with unlimited political bribery being the essence of getting the nominations for president or to elect the president. And the same thing applies to governors and U.S. senators and congress members." - Jimmy Carter, former president, in 2015.
“Allowing people and corporate interest groups and others to spend an unlimited amount of unidentified money has enabled certain individuals to swing any and all elections, whether they are congressional, federal, local, state … Unfortunately and rarely are these people having goals which are in line with those of the general public. History well shows that there is a very selfish game that’s going on and that our government has largely been put up for sale.” - John Dingell, 29-term congressman from Michigan, in 2014 just before he retired.
“When some think tank comes up with the legislation and tells you not to fool with it, why are you even a legislator anymore? You just sit there and take votes and you’re kind of a feudal serf for folks with a lot of money.” - Dale Schultz, 32-year Republican state legislator in Wisconsin and former state Senate Majority Leader, in 2013 before retiring.