Formatting of right hand side of equation should be identical to formatting of left hand side
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"> <mi mathvariant="normal">_ baseline _</mi> <mo>=</mo> <mover> <mi mathvariant="normal">_ baseline _</mi> <mphantom> <mi mathvariant="normal">fail</mi> </mphantom> </mover> </math>