I think you are wrong there. If the GOP removed abortion from the platform, shut up or actively spoke in support of it, and most important voted against the bills that inevitably come from the fringe it would vanish as an issue. The problem is that anyone that cares about it enough to let it sway votes (women) has plenty of examples on that issue when the GOP gets a strong majority. Folks that may not be single issue (at least they don't admit it) use it as one of the many things.
Single issue voters would no longer have that issue as a divisor (among the two major parties at least) if it was dropped from the platform. Would not happen overnight, time would be needed to show that it really was gone but it would go.
Same thing applies to global warming, gays, guns, any other issue that makes people single issue voters. If there is no difference between the major parties on their issue people will either move to third parties, not vote, or find another reason to vote for one of the big two.

The people in charge of of the parties know this and the dividing issues must get enough people motivated to be worth keeping on platforms. At least I hope they are smart enough to do the math but given the recent history of gay marriage I'm not so sure.

As for why the recalls won? The anger was very fresh in the minds of the people at the time so one side was very motivated. We might have seen something very different if it had been a mail in vote, you had to be motivated enough to go vote in person on a Tuesday. Everyone also knew it would not change the control of the state so the message of anger could be sent safely without regard for any other issues. If you believed in gun rights at all you could vote for the recall and all the other issues would remain as they were.