There are certain social issues which distinguish the two major parties. Abortion and homosexual marriage being right at the top. The Republican party will not nominate a pro-abortion candidate for vice-president or president. Same goes with a candidate who is friendly to homosexual marriage. These two issues aren't centrist. They are causes favored by the far Left. I remember the mere mention of God being booed at the 2012 Democratic presidential convention.Abortion isn't going to change based on who is VP or president. They would want a Democrat on the ticket to show that they can work with the other side to solve issues. Right now we need to bring the country back toward the middle where things work well. If you think it will just shift completely to the right like tearing off a bandaid then soon enough we will be talking about Obama being a centrist. There is no perfect candidate out there and you will never agree with any candidate 100% of the time.
The Democrats at the national level are mostly secularists. The Republican party still acknowledges its conservative wing as very much a religious contingent. That being the case, the GOP is respectful towards people of faith. The United States is predominantly a Christian nation. It annoys the Left whenever this is brought up. But, it is true. As a largely Christian nation, it is right that at least one major party reflect the values and traditions which have undergirded our country from its founding.