Hillary Clinton is still ahead in the polls, but she’s far removed from landslide territory. A “50-state poll” isn’t necessarily the same as 50 state polls. And Americans are divided on the best way of keeping the country safe. This is HuffPollster for Monday, September 12, 2016.

CLINTON LEADS NATIONALLY, BUT HER SUPPORTERS LAG IN ENTHUSIASM - Scott Clement and Dan Balz: “Hillary Clinton maintains a lead over Donald Trump, but lagging interest among some of her supporters poses a potential turnout challenge for Democrats with less than nine weeks before Election Day, according to a new Washington Post-ABC News poll…. Trump’s supporters report greater interest in the campaign and voting, which could factor into turnout. More than 6 in 10 registered voters who support Trump say they are following the campaign very closely, and 93 percent say they are absolutely certain to vote. By contrast, 45 percent of Clinton backers are paying close attention to the race, and 80 percent are certain to vote, while one-fifth say they will probably or are less likely to cast a ballot…. Seven in 10 voters say they have “definitely” decided which candidate to support, but a sizable 3 in 10 say they are undecided or might change their mind in the last two months.” [WashPost]

But an enthusiasm gap doesn’t always mean much - Janie Velencia, from May: “Republicans, with the exception of the 2008 election, have always been more enthusiastic about presidential elections, so there’s no historical precedent that suggests any meaningful correlation between voter enthusiasm and the party that wins. Analysts and pundits sometimes rely on enthusiasm level to make assumptions about voter turnout. But doing so is a stretch. Kerri Milita, an assistant professor at Illinois State University who studies voting and elections, notes ‘people who vote will still turn out to vote by and large,’ regardless of enthusiasm…. Instead, other factors such as location and hours of voting stations or the weather are more indicative of voter turnout than reported enthusiasm. As the general election nears, enthusiasm does become an important factor that can help mobilize the base, [University of Michigan professor Michael] Traugott says. But that impact isn’t necessarily direct; it can be useful to ‘tap into voters that have enthusiasm at the grassroots level and get them to work to knock doors, get out the vote,’ as political journalist Ed Kilgore wrote.” [HuffPost]

THE WEEKEND’S POLLS SHOW CLINTON LEADS, NARROW MARGINS - Steven Shepard: “Despite a recent backslide that erased some of Hillary Clinton’s once-yawning advantage in the polls, a raft of national and battleground-state public polling released Sunday gave her a consistent lead against Donald Trump… Clinton’s 5-point lead over Trump among likely voters in an ABC News/Washington Post poll out Sunday morning is an encouraging sign for her campaign — though, like a CNN/ORC International poll last week, it suggests Clinton faces turnout and enthusiasm challenges. Meanwhile, a series of new state-level polls from NBC News/Wall Street Journal/Marist and CBS News/YouGov show that while the race is close in some traditional battlegrounds — like Florida, Nevada and New Hampshire — Clinton has put new red states in play, like Arizona. And a CBS News/YouGov survey in Ohio gives Clinton her largest lead there since before the state’s March primary. Taken together, the new surveys — all conducted entirely in the past week — point to an uphill road for Trump. While he has unquestionably cut into Clinton’s lead over the past few weeks, his support still appears capped at just over 40 percent.” [Politico]

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Recent poll releases:

-NBC News/Wall Street Journal/Marist Arizona: Trump 42, Clinton 41; with Johnson and Stein Trump 40, Clinton 38, Johnson 12, Stein 3. [NBC]

-NBC News/Wall Street Journal/Marist Georgia: Trump 46, Clinton 43; with Johnson (Stein isn’t on the ballot) Trump 44, Clinton 42, Johnson 10. [NBC]

-NBC News/Wall Street Journal/Marist Nevada: Clinton 45, Trump 44; with Johnson and Stein Trump 42, Clinton 41, Johnson 8, Stein 3. [NBC]

-NBC News/Wall Street Journal/Marist New Hampshire: Clinton 42, Trump 41; with Johnson and Stein Clinton 39, Trump 37, Johnson 15, Stein 3. [NBC]

-CBS News/YouGov Florida: Clinton 44, Trump 42, Johnson 5, Stein 2. [CBS]

-CBS News/YouGov Ohio: Clinton 46, Trump 39, Johnson 7, Stein 2. [CBS]

-CBS News/YouGov 13 battleground states: Clinton 43, Trump 42, Johnson 6, Stein 2. [CBS]

-RABA Research/Simpson College Iowa: Trump 40, Clinton 39, Johnson 10, Stein 3. [RABA Research]

-ABC News/Washington Post national: Clinton 46, Trump 41, Johnson 9, Stein 2. [WashPost]

-Morning Consult national: Clinton 41, Trump 39, Johnson 10, Stein 3. [Morning Consult]

HOW HUFFPOST POLLSTER AGGREGATES POLLS - HuffPollster: “Readers may wonder how does the HuffPost Pollster model work and why isn’t our estimate of Hillary Clinton vs. Donald Trump exactly the same as that of other polling aggregators. Here’s how and why. The HuffPost Pollster charts for this year’s general election contests estimate the “average” of publicly available polls that meet our criteria for quality polling. HuffPost uses a Bayesian Kalman filter model... Briefly, Kalman filter models combine data that are known to be “noisy” ― or not completely precise ― into a single estimate of the underlying “signal” ― that is, what’s actually happening. For HuffPost, that means the model looks for trends in the polls and produces its best estimate of the polling average.” [HuffPost]

THERE’S A DIFFERENCE BETWEEN 50 STATE POLLS AND A “50-STATE POLL” - Nate Silver: “It sounds like a riddle of sorts: Is one giant poll of all 50 states the same thing as 50 small polls, one for each state, added together? If this seems like an odd question, it’s because it hadn’t really come up before this year. Sure, technically speaking, any national poll is composed of interviews from all 50 states… But what if instead of using a sample size of 1,000, your poll interviewed 50,000 people? Now you’d have around 5,000 respondents from California and 1,500 from Virginia — more than enough to go around…. Is a 500-person subsample of Colorado voters from a 20,000-person national poll the same thing as a 500-person poll that was dedicated to Colorado, specifically? After thinking and researching my way through the problem, my answer is that these polls aren’t quite the same. The Colorado-specific poll is likely to provide a more reliable estimate of what’s going on in that particular state. And it deserves a higher weight in our model as a result. One reason to give the 50-state technique a lower weight is that hasn’t really been empirically tested…. One potential source of error has to do with demographic weighting…. Another potential problem is misidentifying the state a poll respondent votes in.” [538]

A relatively new statistical technique is boosting the predictive power of 50-state polls - David Rothschild: “There are trade-offs and benefits to collecting samples across the country at one time, but the key reason to do a single 50-state polls is that data analysis has evolved to make it very accurate and cost-effective to analyze all 50-states at the same time…. [Silver] determines that the data collection is less accurate…. [W]ith the right analytics, national samples may actually make more accurate forecasts for the 50 states than 50 state polls…. [T]he more biased the sample, the more modelling and post-stratification (MRP) does better than raking. MRP makes a very elegant assumption: you can learn something about the sentiment of white men from Kentucky by looking at white men from West Virginia. Or, more generally, you can learn something about the sentiment of any person by considering, independently, all of the demographics that define that person: age, gender, race, education, party identification, and, of course, geography…. MRP further takes advantage of the relative stability of votes in any given year and region to model voter turnout with historical data, as well as the data from a given poll.” [PredictWise]

AMERICANS ARE SPLIT ON HOW TO KEEP THE COUNTRY SAFE - HuffPollster: “Fifteen years after the 9/11 attacks, Americans are close to evenly divided on whether it’s better for the U.S. to actively confront terrorism or to take a more isolationist approach, a new HuffPost/YouGov survey finds. A 53 percent majority says that, in the long run, the United States will be safer if it confronts the countries and groups that promote terrorism. Forty-seven percent say the United States will be safer from terrorism if it stays out of other countries’ affairs. The results mark a shift since 2013, when an Economist/YouGov poll found that 61 percent of Americans favored staying out of other countries’ affairs, with just 39 percent advocating taking action against countries and groups promoting terrorism. While Democrats and independents have both moved toward the latter position since then, the biggest move was among Republicans. Seventy-six percent of Republicans now say the U.S. should intervene against those countries and groups, up 21 points in the past three years.” [HuffPost]

MONDAY’S ‘OUTLIERS’ - Links to the best of news at the intersection of polling, politics and political data:

-Alex Isenstadt writes that internal polls have some GOP candidates worried about Donald Trump’s downballot effect. [Politico]

-Harry Enten notes that Hillary Clinton is still having difficulty winning over millennials. [538]

-Yancey Roy cautions that presidential debates usually do little to move the polls. [Newsday]

-Gallup finds that 62 percent of Americans are confident in the accuracy of the vote count this year. [Gallup]

-CNN/ORC puts Americans’ economic outlook at a 9-year high. [CNN]

-Philip Bump introduces a rating system for different types of polls. [WashPost]

-Slate’s Julia Turner explains why the outlet plans to team up with a startup called Votecastr to publish estimates on Election Day; Votecastr chief strategist Sasha Issenberg provides more details about the methodology. [Slate Part 1, Part 2]