Democratic presidential candidates Hillary Clinton and Bernie Sanders have been sparring lately about the degree to which large donations to Clinton's campaign may have influenced any decisions that she might have made. That debate misses the point of campaign contributions.

I expect that it is seldom the case that a donor walks into a politician's office and demands that he or she vote a certain way on a particular bill in exchange for a campaign contribution. It may be controversial to say, but I think most politicians are honest enough to reject such outright bribery. But if contributions don't buy votes, then why would companies and influence groups spend so much on them? Sanders is right to ask that question, but he seems to have missed the real answer, which is that contributions buy the right for the contributor to make their case in a more detailed way directly to the political representative.

When I was on my high-school debate team, we argued a single proposition over and over each year. I learned how to effectively represent either side of the question. It got to the point where I no longer knew which side I actually favored because there were always multiple ways to look at any complex public issue. Campaign contributions result in politicians hearing one side of each policy debate at great length as presented by a skilled debater. They don't change their opinions as a result of this, they form them. So I believe Clinton when she says that she never changed a political decision as a result of a campaign contribution — but she almost certainly became convinced that one side of an issue was more correct than the other or that one solution to a problem was better than another as a result of considering what contributors' lobbyists had to say without hearing equally well-prepared counterarguments.

One reason our society has become so polarized is that the proliferation of Internet and cable news sources, including various social-media outlets, provides so many places to hear views that we no longer have to hear both sides of any issue. We can choose to listen only to arguments that reinforce what we are already inclined to accept and are never forced to consider carefully reasoned opposing arguments. When news outlets were much more limited, they often played the role of moderator in public debates, but that is now rarely the case. Our political representation has become similarly polarized because large campaign contributions result in politicians who only hear arguments on one side of each issue. That is the last thing that we need right now.

Paul Krueger is retired and living in Minnetonka and publishes an occasional macroeconomics blog called "Civil Discourse."