But one reason that McCain emphasized his "maverick"-ness in OTL in 1999-2000 is precisely that he knew the GOP Establishment was pretty solidly behind Bush. If Bush were not in the field, McCain might put much more emphasis on the many issues on which he was a pretty standard conservative Republican (including abortion) and much less on the few issues on which he wasn't (notably, campaign finance). So he might have been seen as a "mainstream Republican." Of course there might be rivals for "mainstream Republican" support--Liddy Dole or John Kasich or John Engler, for example--but they all had political disadvantages of their own, in terms of not being widely-enough known or in the case of Liddy Dole of being married to the man who had lost in 1996...