Nate Silver: High Number of Undecideds, Uncertainty at First Debate

As the presidential campaign heads into the first debate Monday, a study of the most recent polls shows that the race is both close and uncertain, with Democratic candidate Hillary Clinton holding a slim advantage over Donald Trump, according to Nate Silver's FiveThirtyEight.com.

Clinton is considered a 58 percent favorite to win the election. In the Electoral College count, the Democratic nominee is leading in the states she needs to capture, but not by a very large margin, and Trump is not far behind in several of the key states he needs to win in order to turn the tide.

A major source of the uncertainty is the high number of undecided voters at this stage of the campaign. The Huffington Post reported that at this point in 2012, Obama led Mitt Romney 48 percent to 46 percent; Clinton is ahead of Trump by about 42 percent to 40 percent.

This means that some 18 percent of the electorate is undecided, compared to only 6 percent at this point four years ago.

As FiveThirtyEight points out, the race is so tight that if the election was held today and Trump emerged as a narrow winner, it would not be considered a major polling error, although either a Clinton landslide or a solid Trump triumph would show that the surveys were inaccurate.

Despite some Clinton gains in the latest polls, the general trend has been with Trump, who has narrowed Clinton's lead from its peak of 8 percentage points in early August to the current 2 percent advantage.

But the most important factor is that there are more swing states up for grabs this election than has been the case in recent elections, which makes the entire result so uncertain because polling errors in a few of these locations could alter the whole Electoral College math.

A key element in this uncertainly is that Clinton's position, even in swing states she is leading, has not been particularly strong because those locations tend to have a high proportion of white working-class whites, which is the demographic group in which Trump is the strongest.

• Clinton, Trump in Dead Heat Heading into First Debate
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