美总统选举为何难分胜负？

美国总统选举在短短一个月内选情出现急剧变化。具体讲，很多人原本认为现任总统奥巴马(Barack Obama)必将获胜，但如今却变得似乎难分胜负。		The presidential campaign has traveled a long way in one short month. Specifically, it has moved from what many considered an inevitable victory for President Barack Obama to what now appears to be a dead heat.

选情生变有两种可能的解释。一种解释对奥巴马更为有利，而另外一种则对他的对手、共和党总统候选人罗姆尼(Mitt Romney)更为有利。无论如何解释，选情的变化实际上都非常小，但对于这样一场难分胜负的竞选来说，微小的变化可能起到决定性的作用。		There are two possible explanations for this evolution. One is more favorable to President Obama. The other is more favorable to his Republican challenger, Mitt Romney. In either case, the movements actually are pretty small─though small movements can be decisive in a race this close.

有鉴于此，在距离大选之日还有整整两周的时候，让我们逐一分析一下这两种可能的解释，因为它们可以从很大程度上向我们揭示未来的可能情况：		So, with precisely two weeks to go before Election Day, let's examine those two possibilities in turn, for they can tell us an awful lot about what might lie ahead:

眼下的局面只是将注定势均力敌的选举不可避免地变得胶着。		What we've seen is merely the inevitable tightening in what was always destined to be a close race.

按照这种更有利于奥巴马的解释，民调所显示出的选情变化是预料之中的，眼下只是最终注定要支持罗姆尼的选民开始真正站到他那一边。		In this interpretation, the one more favorable to President Obama, the movement that we've seen in the polls has been the predictable settling of voters into slots they were destined to occupy in the end.

选情的胶着并不意味着在第一场总统辩论会后情况出现了一些基本转变。人们普遍认为罗姆尼在第一轮辩论中胜出。那场辩论带来的结果只是加快了那些终将站到罗姆尼一边的选民行动起来。他们得到了最终可能得到的结果，只是比预想的早一点。		This tightening of the race doesn't reflect some fundamental shift after that first presidential debate, widely seen as won by Mr. Romney. All that debate did was speed up the movement of voters who were destined to land in Mr. Romney's column anyway. They got where they were going, just a little earlier than otherwise.

事实上，奥巴马的助手们正是这样说的。		That, in fact, is precisely what aides to Mr. Obama say happened.

在《华尔街日报》和NBC News过去两个月进行的民调中可以找到一些支持这一观点的证据。近几周来开始支持罗姆尼的一些选民确实来自他原本的支持者群体。		And some evidence for this view can be found in Wall Street Journal/NBC News polling over the last two months. Some voters who have moved toward Mr. Romney in recent weeks do, indeed, come from within his natural base of supporters.

举例来讲，在罗姆尼对奥巴马的民调中，罗姆尼在自称保守派的选民中的支持率从9月初的76%上升至目前的80%。罗姆尼在白人福音派选民中的支持率从78%上升至82%。白人福音派选民是罗姆尼支持者群体中的一个强有力的组成部分。		Support for Mr. Romney among self-described conservatives in a matchup with Mr. Obama, for example, has risen to 80% from 76% between early September and now. Support among white evangelicals, who have turned out to be a powerful component of Mr. Romney's base, has moved up to 82% from 78%.

罗姆尼在白人男性选民中的支持率从58%上升至62%。白人男性选民是现今共和党支持者群体的真正核心。		And his support among white men, the real core of today's GOP, has risen to 62% from 58%.

在某个时期，这些群体对罗姆尼的支持都一直很强──实际上，在像今年这样选民严重分化的情况下，对于任何共和党总统候选人都是如此。		These are all groups that always figured to be strong for Mr. Romney─indeed, with any Republican nominee, in this year of a polarized electorate─at some point.

这似乎重现了2004年美国大选时的情形。当时，同样激烈的选战对在任总统小布什构成了巨大挑战，小布什的部分领先优势在第一场辩论之后蒸发，不过他仍然赢得了大选。		This scenario sees a repeat of what the nation experienced in 2004, a similarly close race in which an incumbent president facing a big challenge, George W. Bush, saw his lead evaporate after the first debate but held on to win.

此外，这些变动中有些来自罗姆尼已经注定会拿下的州，这些变化推高了他在全国民调中的支持率，但是不会真正影响九个摇摆州的结果，而这九个州才是决定选举结果的关键。		Moreover, some of this movement has come in states Mr. Romney already was destined to win, driving up his numbers in national polling but not really affecting the outcome in the nine swing states that will determine the election.

另一种解释是，我们所看到的是奥巴马颇具竞争力的地位开始慢慢瓦解，而这个过程在接下来的最后两周将继续下去。		What we've seen is the beginning of a slow erosion of Mr. Obama's competitive position that will continue over the final two weeks.

这种解释显然对罗姆尼及其所在的共和党有利，对奥巴马则可能是致命的。		This, obviously, is the explanation favorable to Mr. Romney and his Republicans─and potentially fatal to Mr. Obama.

在这种情形下，没有决定投票倾向或是立场不坚定的选民不断地开始转向支持罗姆尼。		Under this scenario, what we've seen is the steady movement of people who are either undecided, or whose support for one candidate or the other was very mushy, breaking steadily for Mr. Romney.

若真是这样，那么这些变化就意味着，如果摇摆选民现在仍然没有决定支持现任总统，实际上他们就已经决定不会再支持他了，他们只是需要适应自己将支持罗姆尼的决定。		If that's correct, then the movement suggests that, if swing voters haven't decided to support the incumbent president by now, they've actually decided they can't support him. They merely needed to get comfortable with the alternative before moving.

�华尔街日报》和NBC News民调中的一些结果支持了上述观点。首先，过去几个星期，独立人士更加倾向于支持罗姆尼，尤其是白人独立人士。罗姆尼在白人独立人士中的支持率从51%上升到了56%，而奥巴马在这一群体中的支持率从40%下降到了30%。		There also is evidence to support this theory within Journal/NBC News polling. For starters, independents have drifted more toward Mr. Romney over the last few weeks, particularly white independents. His backing among them has moved to 56% from 51% while support for Mr. Obama has fallen to 30% from 40%.

与此同时，罗姆尼在工会家庭选民中的支持率从34%上升到了40%。他在未婚白人中的支持率从46%上升到了49%，而奥巴马在这一群体中的支持率从50%降到了44%。		Similarly, Romney support in union households has moved to 40% from 34%. His support among nonmarried whites has ticked up to 49% from 46%, while support for Mr. Obama has moved down, to 44% from 50%.

换句话说，奥巴马在一些中间选民群体中的支持率已经下滑，部分原因是一些立场不坚定的支持者以及这些群体中一些未做决定的选民转而开始支持罗姆尼。		In other words, the president's standing among some groups in the middle of the electorate has eroded, partly because of some movement away from him by soft supporters and partly because undecided voters in these categories have drifted to the GOP column.

如果这种分析正确的话，奥巴马的支持率可能不足50%，而迟迟未作出决定的选民正在放弃对他的支持。持这种观点的人士乐于回忆1980年的大选。当时，在人们逐步适应里根(Ronald Reagan)当总统的观念后，最后的选情开始朝着不利于在任总统卡特(Jimmy Carter)的方向发展，倒向了共和党的挑战者里根，这些变化决定了大选结果。		If this scenario is correct, Mr. Obama may have topped out just short of 50%, while late-breakers are moving away from him. Believers in this scenario like to think back to 1980, when movement at the end was decidedly away from the incumbent, Jimmy Carter, and toward the Republican challenger, Ronald Reagan, once people got more comfortable with the idea of a President Reagan.

必须要强调一点，所有的这些变化都只代表着一个维持微妙平衡的选民团体中发生的微小改变。		It's important to underscore that all of these movements represent small changes across a finely balanced electorate.

这样的微小改变只在一个时候显得格外重要，那就是大选当天。

Such small movements can look big only once─on Election Day.