Sentence:  A system for creating software that runs, unaltered, on all sorts of computers and devices . . . could transform the software business in the network era from a <WSD>one-horse race</WSD> led by Microsoft to a true contest. 
Meaning of the word marked with <WSD> tags:  An election campaign or other competitive situation in which only one competitor is entered or in which only one competitor has a realistic chance of winning.