But according to the polls, so does opposition to gay marriage -- an issue on which Bush agrees with basically every other candidate.
The polls, in fact, show that about half of likely GOP caucus and primary voters in Iowa, New Hampshire and South Carolina said they find opposition to gay marriage either "mostly" or "totally" unacceptable in a candidate. Fifty-two percent of likely Republican primary voters in New Hampshire and South Carolina said opposing gay marriage is either mostly or totally unacceptable, while 47 percent of likely Iowa caucus voters agree.
By comparison, 63 percent of Iowa voters say belief in man-made climate change (and fighting it) is unacceptable, 56 percent of New Hampshire voters say raising taxes on the wealthy is a non-starter, and 52 percent of South Carolina voters say support for comprehensive immigration reform that includes a path to citizenship is a deal-breaker on one level or another.
Voters in all three states find a candidate who supports gay marriage to be about as amenable as one who doesn't toe the party line on any of these issues.
And while the numbers are surprising, they make some sense. A Pew poll conducted in March 2014 showed 39 percent of Republicans and Republican leaners supported gay marriage. Add the passage of time and the fact that non-Republicans can vote in New Hampshire and South Carolina, and you've got a potentially less anti-gay marriage electorate come next year.
There's also the possibility that the poll question confused some people. Asking people about gay marriage opposition rather than support for it brings double-negatives into the picture, possibly confusing some poll respondents. And people are more apt to respond in the negative when in doubt.
But it's also pretty clear from this and other polls that there are a growing number of Republicans who support gay marriage. So does it all mean we'll see a GOP presidential candidate in 2016 come out in support of gay marriage? Probably not. While there are some supporters of immigration reform (see: Bush and Marco Rubio) and Common Core (Bush) in the group, the name of the game is alienating as few people as possible.
You also have to wonder just how much of a deal-breaker gay marriage support is. The poll asked about opposition to gay marriage -- not support -- so it's a little harder to suss out just how many people would vote against a candidate who supports gay marriage. We're guessing it's still more of a voting issue for those who oppose gay marriage than those who support it -- at least on the GOP side. (For what it's worth, though, between 25 and 31 percent of likely GOP voters in each state say opposing gay marriage is "totally unacceptable" -- a number that is on-par with all of these other issues.)
And then there's the matter of nobody wanting to be the first candidate to stick his or her neck out.
But regardless, it's fascinating that this many likely Republican primary and caucus voters in the earliest states (especially socially conservative ones like Iowa and South Carolina) say they find opposition to gay marriage being unacceptable.
And it's a sign of just how quickly this country -- and even the GOP -- is moving toward embracing it.
Updated at 8:03 a.m.