Complicating the matter for senators is the Trump campaign’s decision to not engage, so far, in the traditional transition process, having declined to sign agreements with the federal government that would launch FBI background checks of nominees, among other standard steps before confirmation hearings.

The president-elect is testing the loyalty of Republican in Congress, leaving even his close allies nervous about the unpredictability and upheaval to come.

If Trump nominates a candidate whom Democrats uniformly oppose, he can lose only three votes from his own party. Here's who to watch.