[indubitable]

Smaller candidates today already stand stand practically 0 chance of getting elected. Literally every single member in the house of representatives is either a democrat or a republican. That is a consequence of a simple question: 'If a person receives 10% of the vote in a state with 10 representatives, how many seats should they receive?' The current answer is 0.

In our current system the one and only power of smaller candidates is a spoiler effect. This enables them to have some influence on the super-party that's closest to their own ideology, even if implicitly. Rank preferential / Australian voting / etc not only fail to change the 10% support = 0% representation issue, but they even remove the spoiler effect which means that smaller parties can safely be completely ignored unless they look to gain a plurality themselves - which is rather contrary to the notion of smaller.

On this note, I'm not seeing why you think that proportional would make campaigning more difficult for 'smaller candidates.' It would mean they might actually stand a chance of finally getting a seat in congress. A basic example from Europe would be something like 'The Pirate Party.' They're never likely to gain substantial support, but they have been able to receive representation at the national level in a variety of nations, proportional to their support, exclusively due to proportional systems.

[KGIII]

Sanders and King are both Independents but caucused with the Democrats.

This doesn't really negate your point, I just figured you may be interested. They may not literally all be a D or an R, but it's trivial and I'm mostly being pedantic.

[Armisael16]

If we're being pedantic, both Sanders and King are senators.

[KGIII]

Right, my bad. I read that as congress. I'm nit sure why I missed the specificity, considering I read it twice and then looked up the information on Wikipedia.

My bad, indeed.