At least 20 Republicans from blue states want to keep the deduction for state and local taxes, the elimination of which is a major part of most Republican tax-reform plans. (It was even part of the 1986 plan, originally.) Ryan Ellis lays out a few ideas on making a limit to the deduction politically palatable; I especially like his second and third ones.
If tax reform included an expansion of the child credit, it could further soften the blow for blue-state Republicans. Check the graph in Ellis’s article to get a sense of why that probably is.