It is, as you say, so that I can have a meaningful voice in local primary elections, where many important local races are actually decided, because of the overwhelmingly Republican nature of the community in which I live. Pennsylvania is a closed primary state.

I have stated that many times ("many" being defined as "more than three"). I haven't gone back to telling this story because I told it several times, and I didn't want to be boring, but since you missed it:

I finally changed my registration to Republican the year that the religious right took over our school board and attempted to alter, among other things, our sex education curriculum and the biology curriculum regarding (surprise!) evolution. The only effective way to fight them was to organize in a way that the general population could support, and to defeat them in the Republican primary. To vote in the Republican primary I had to register as a Republican. It was, and is, more important for me to be effective politically with my most important tool, my vote, than it is to remain politically pure, an oxymoronic expression at best.

The first rule of political action: If you're comfortable with everyone at the table, your coalition is too small. So I can deal with Republicans if we have a common cause, even to the point of pretending to be one. Nevertheless: the second rule of political action: If you accomodate those you oppose to the point of losing your own identity, you are no longer in opposition. Join your opponents. I haven't gotten there, but I think maybe Gary has.