The difficult part is determining who is more likely to win in your congressional district. The likelihood of good polling on that level being available to the public is virtually nil.
If you are not able to get a good sense of how your congressional district is leaning, it may make sense to make your decision on other factors.
For instance, if a candidate makes a stop in your area and it is rather out of the way, that may be an indication that internal polling is showing that candidate doing well there. Also, taking into account the areas where each candidate has done well demographically may work. If you are in an upscale or strongly Mormon area, voting for Romney would probably make the most sense strategically. If you live in an area with a strong evangelical constituency or a lot of transplanted Southerners or more blue-collar or working class or more rural with hunters and strong 2nd amendment support, then Huckabee would probably stand a better chance.
In broad terms, I would guess Huckabee is the best bet in the Central Valley and the foothills. Romney would probably be better in upscale urban enclaves. The suburbs of the big cities would vary widely based on local nuances.
California is giving out GOP delegates by congressional district this year. So to follow your strategy of stopping McCain, conservative voters would need to look at whether Huckabee or Romney has the better chance in their area and vote accordingly.
From the clip it is clear that when he says “freedom from religion,” he is speaking of an individual’s right not to believe in God. He then goes on to say that for someone to say it is inappropriate for those with faith to speak about God in the public square defies our civilization, our culture and our citizenship.