Listen to a good speech delivered by former Gov Haley Barbour to BlogBash 2012 attendees at the GOP convention in Tampa. He tries to explain to those who don't understand the strategy of politics - some more strident Tea Party and those who may identify as conservatives but not Republicans - and declares himself a proud "Establishment Republican".
"70 million voters have to get under our tent. I beg you to make it as easy for them as possible."
Purity does not win elections, nor does it grow a political party. If you consider Ronald Reagan a political model, you must remember his philosophy that he considered someone agreeing with you 80% of the time as a partner.
Here is the video. It is worth the time. (Ignore the loud woman who keeps butting in with dumb remarks - Haley does!)