I don't think the Republican Party needs to be abandoned. Nor does it need to be blindly supported. Instead, in a manner akin to Grover Norquist's no tax pledge, lovers of liberty need to work out a simple pledge to support the US Constitution and require candidates to support it. If those candidates feel the need to run under the umbrella of the GOP, that's fine - they should not be penalized for adopting a label. If those candidates decide to run as Libertarians or Independents, then likewise - the label is not important. The pledge is.
When a candidate decides to support unconstitutional legislation, or backs a huge and horrible bill because there is something in it he likes, he loses the support of the lovers of liberty. Maybe the GOP can save him, maybe they won't both. We don't care. We'll be supporting the next candidate who does.
The GOP is just a tool. We can use it, sometimes, when necessary. But all of our candidates need to oppose unconstitutional legislation and administrative overreach as a first principle, whatever label they choose to adopt.