<<< native [ EUnder False (EIdentifier "_ baseline _") (EIdentifier "under script") , ESymbol Rel "=" , EUnder False (EOver False (EIdentifier "_ baseline _") (EPhantom (EIdentifier "fail"))) (EIdentifier "under script") ] >>> mml $$\underset{\mathrm{under\; script}}{\mathrm{\_\; baseline\; \_}}=\underset{\mathrm{under\; script}}{\stackrel{\phantom{\mathrm{fail}}}{\mathrm{\_\; baseline\; \_}}}$$