Citizens United v. Federal Election Commission, 558 U.S. 08-205 (2010) was a landmark case that effects every American citizen and taxpayer. The Supreme Court ruling grants first amendment rights to corporations, allowing them to donate to political campaigns. Through a 501(c)4, any corporation can now funnel unlimited amounts of money to a SuperPAC and therefore a candidate. Though SuperPAC's are not allowed to "coordinate" with candidates directly, they are allowed to air advertisements supporting and now including candidates.
This unlimited filtering of corporate dollars into government is drowning out the voice of the citizens of the United States and creating a government no longer for the people and by the people.
A Constitutional amendment is the only way to overturn the ruling