From what I understand, speech restrictions are upheld in very narrow ways:
- "time, place, and manner" restrictions such as not yelling at 4 AM in a residential area (these must withstand what's called "immediate scrutiny", which basically says that the restrictions must be content neutral, narrowly tailored to serve a specific government interest, and leave ample opportunity to share outside of the specific circumstances)
- "content" restrictions, such as restrictions on direct threats or child porn. These must pass strict scrutiny (narrowly tailored, serve a specific government interest, and be the least restrictive means to serve that interest.)
The government's interest has never been in "remedying" the problem of people speaking about politics, regardless of money (it does have an interest in stopping bribery, but that's a different issue.) Indeed, Kennedy's majority opinion in Citizens United is quite direct about wanting to allow more people to speak about politics -- specifically, allowing associations of people (ie, corporations, unions, etc.) the same ability to speak that single wealthy individuals have. The alternative to CU is frightening -- the only people whose political messages could be heard would be the few with the money to own media companies, or the few with the social networking apparatus to create faux-viral content.
This parallels older supreme court decisions such as:
Dartmouth College v. Woodward, 17 U.S. 518 (1819)
Providence Bank v. Billings, 29 U.S. 514 (1830)
Santa Clara County v Southern Pacific Railroad Company, 118 U.S. 394 (1886)
United States v. United Auto Workers, 352 U.S. 567 (1957)