Depends on the person. Some people are more compatible than others. Some people are nicer than others. Some people are more accepting of others.
What is important is to speak each other's "love language". What is important is to communicate concerns and compromise. What is important is to continue to love each other.
"Love" is not an abstract concept or word only. Love is also a verb! It is very much possible for complete opposites to attract IF each person can do all of the above. Perseverance, understanding, and patience are all necessary virtues for a successful marriage.
Having different and strong political beliefs makes for much better conversation. Where other couples do a:
Wife: "hey, how's your day been?"
Husband: "Good, boring at work..but good. What about yours?"
Wife: "I went shopping with Sarah and I paid the bills..nothing else though."
politically contrasted couples can debate politics in a RESPECTFUL manner. It can be very very fun and can make you better friends. Being best friends with your spouse is not a bad thing and I recommend it.
Religious beliefs, however, can get in the way. This is a toughy. If one of you is a devote Jew, there ain't gettin' married until you both are lighting 9 candles. If you want to marry a devote LDS women, you had better be a Mormon yourself...etc.etc.
Even that can be gotten around through mutual acceptance.
Though, on top of all of it...it is sooooo much easier if the couple has in common political and religious beliefs.