The necessary tension between democratic capitalism and republican government is another in our series of ongoing balancing acts. In recent years, the cost of campaigning has escalated. The ability to raise money becomes the defining hurdle of who is a convincing candidate. Politicians who can raise more money get their message out more effectively. The best-financed candidate doesn't always win, but has an edge.
Incumbents tend to benefit disproportionately.
As politicians pander more and more to donors and have less and less time for ordinary voters, democracy itself is compromised. The ideal of an informed electorate debating the public good becomes ever further removed from the grubby reality. This is not to say, of course, that democracy can or should exist without interest groups, or that interest groups shouldn't enjoy free speech. But an interest group that commands a politician's attention because it has aggregated millions of voters is somehow closer to the democratic ideal than one whose influence is based on writing a large check. When private donations finance campaigns, money plainly buys influence.