Since the 1970s, electoral politics has gotten much more expensive (in real terms). As political scientist Thomas Ferguson and others have argued, modern political parties have adapted by granting leadership positions to those members best able to bring in large contributions—a strategy pioneered by Newt Gingrich but since slavishly imitated by the Democrats.
The result is that the parties’ platforms now reflect the wishes of their major funders, not their median voters. This is why Republican presidential candidates spent the primary season competing to offer the most generous tax breaks to the rich—while Paul Ryan’s budget slashes Medicare, a program supported by the Tea Party rank and file. For the rich people who call the shots, it’s simply in their interest to lower taxes on the rich and raise them on the poor. End of story.James Kwak, The GOP’s Bizarre, Disturbing Passion for Raising Taxes on the Poor