Kevin Phillips in his *William McKinley* (New York: Times Books 2003) argued that with the possible exception of Iowa Senator William Allison, the GOP alternatives to McKinley would very likely have lost--*especially* Reed:
"In all likelihood, no other Republican could have done as well as McKinley. Certainly not porcine House Speaker Reed, whose Yankee drawl, acerbic wit, and longtime support for gold would have fit into an Eastern stereotype to voters west of the Appalachians. Simply subtract from McKinley's total the reasonably close states of California, Oregon, Indiana, Ohio, and North Dakota--all political cultures where Reed's Eastern orientation would have played into Bryan's hands--and the House Speaker would have been defeated. Probably he would not have done that well." (p. 76) (I would add that I doubt that Reed would have carried Kentucky, either.)
If he did win, presumably the big difference between him and McKinley would be his opposition to the Spanish American War.
All in all, though, I think it unlikely that Reed will be nominated. The Republicans were well aware that the safely anti-Bryan East was not the battleground, and that a Midwestern candidate would be the best bet to defeat Bryan. And they were absolutely desperate to defeat Bryan...