Yes, the majority of the US citizens are Protestant Christians.
Many Protestant Christians in the USA believe that the US government is against them.
The fact that there is not a single Protestant Christian in the US Supreme Court is proof positive for many Protestant Christians that US government is out to get Bible-believing Christians.
If Donald Trump nominates a non-Protestant Christian to the US Supreme Court, then Trump will have a lot of problems in the next four years. Protestant Christians will believe that Donald Trump is a part of the anti-Christian Washington DC establishment.
Many Protestant Christians in America are willing to fight and die for Christ to defend the true Gospel of Jesus Christ against all earthly powers. If Trump nominates anyone other than a Bible-believing Protestant Christian to the US Supreme Court, then US government will face exponential growth in resistance among “law-abiding” US citizens.
It is important for Donald Trump to show that he is not a puppet for Atheists or Jews or Muslims. It is important for Donald Trump to show that he will stand with America’s Protestant Christian majority. This is the way he will be a true leader of America’s majority. Democracy is majority rule.