If Republicans in the House and Senate fail to pass tax reform by the end of the year, they could see conservative outside groups like Americans for Prosperity pulling some of their financial support in 2018 to focus on state-level races, AFP's President Tim Phillips told Axios.

Why it matters: The Koch brothers, who fund AFP, have some of the deepest pockets of GOP's supporters. While Phillips is optimistic that tax reform will happen by the end of the year, the pressure is on. If tax reform ends up like health care, the Republican party will be in crisis.

"If you have a Congress that's failing at everything," he said, "Then you can see groups reasonably deciding to put more emphasis on gubernatorial efforts or state legislative efforts where you're seeing genuine policy achievements as opposed to Washington where they're not."