The scriptures instruct us how to deal with unbelievers in the world.
1 Cor 5:9 I wrote unto you in an epistle not to company with fornicators:
10 Yet not altogether with the fornicators of this world, or with the covetous, or extortioners, or with idolaters; for then must ye needs go out of the world.
The scriptures are very practical. The Lord knows we are in a world full of fornicators, the covetous, idolaters, etc... It is impossible to avoid all contact with these persons, else we would have to leave the world itself.
Do you fail to buy groceries because the man who owns the store is a Muslim? No. Do you fail to buy clothes because they were made in China by Buddists? No. Do you fail to buy a car because the man who owns the car company is Catholic? No. Do you fail to work because the man who owns your company is a Episcopalian? No.
There is just no way to avoid unbelievers. God does not expect us to avoid all unbelievers, but he does expect us to act differently from them and not to partake in their sins.
If you try to avoid all unbelievers you end up like one of these sects, living in isolation from the world. We are not instructed to do that. We are allowed to have contact and conduct business, etc... with unbelievers.
I would love to have a godly Christian President, but there is not one on the ballot. So, you have to choose what is best for the country.