Today we have the Heritage Foundation and other think tanks with an undeniable partisan bent, the Koch Brothers, Rupert Murdoch, and so on. Their influence on national-level elected officials on down to your Uncle Bob in Wichita has been rather profound.
Were there similar goings-on back in the days of Rockefeller and Vanderbilt? Was there a Victorian equivalent to the so-called "Koch-topus"? What was there? I imagine there was something, if not nearly so sophisticated and orchestrated.
There are several answers to your question, all of which are yes.
As far as media goes, back in those days, not unlike Fox, news was biased based on bias. You would not read a 'neutral' source, if you were a democrat, you bought the democratic paper. While more unbiased sources were developing then, they were in the minority. Thus, if you wanted saber rattlers, look toward the muckraking yellow journalists. Joseph Pulitzer and William Randolph Hearst were the biggest game in town and they had a biased story to sell you. Their journalism combined is often credited (at least in part) for committing us to the Spanish American War.
If you are looking for the fundraising side, look to Mark Hanna. While Rockefeller and JP Morgan hated each other, a lot, they were brought together to crush the populist democrat William Jennings Bryan, who they thought would ruin their wealth by fighting against corporations and moving them to the bimetallism (silver and gold standards, instead of just gold). In response, Hanna convinced Rockefeller and Morgan to give $3.5 million to the campaign of McKinley, the equivalent today of between $866 million to $3.8 billion depending how you calculate, outspending Bryan 5 to 1.