HUFFPOLLSTER: Could Democrats Win The House Majority?

It’s possible, but Clinton would need to win by a lot to have that much of a coattail effect.

Hillary Clinton would have to win by a lot to help Democrats gain the House majority. Oversampling is a valid and often-used technique in polls. And Clinton’s support is growing among young voters. This is HuffPollster for Tuesday, October 25, 2016.

A CLINTON WIN MIGHT NOT BE BIG ENOUGH TO FLIP THE HOUSE - John Harwood: “The larger Hillary Clinton’s polling margin over Donald J. Trump grows, the louder the question becomes: Is control of the House of Representatives really in play? Among House strategists in both parties, the answer remains the same as it has been all year: not yet. Democrats must gain 30 seats to capture a majority. That requires sweeping nearly all Republican-held seats in which they nurse even small hopes of winning. Yet the interplay between the presidential race and others on the ballot has made those small hopes bigger….Using data from elections since 1948, [Columbia University’s Robert] Erikson estimates the coattail effect this way: Every percentage point added to a Clinton victory margin would add half a point to the average Democratic House candidate….Gary Jacobson of the University of California, San Diego, uses generic vote poll questions to predict House outcomes. In his calculation, which subtracts those who are undecided, voters now say by a margin of 53 percent to 47 percent that they want Democrats to control the House next year. House Democrats need to stretch that edge to around 55-45 percent to come within range of a majority, he estimates. And to do that, they need a Clinton victory margin larger than the roughly six-percentage-point polling margin in the current New York Times national average.” [NYT]

FORECAST UPDATE - Hillary Clinton has a 96.6 percent chance of winning the presidency. Republicans’ chances of keeping the Senate majority are declining ― they’re down to a 30 percent chance of getting 51 or more seats, Democrats have a 35 percent chance of getting 51 or more seats and there’s a 35 percent chance that the chamber will be split 50-50. Accounting for Clinton’s 96 percent chance of winning the presidency, which would make Tim Kaine vice president and the tie-breaking vote , that becomes a 69 percent chance of Democrats taking over. [Senate forecast, Presidential forecast]

ATTACKS ON POLLS FOR “OVERSAMPLING” ARE BASELESS - HuffPollster: “Donald Trump’s campaign has highlighted some of the finer, typically ignored points of polling this year, usually by boisterously misunderstanding them. ‘WikiLeaks also shows how John Podesta rigged the polls by oversampling Democrats ― a voter suppression technique,’ the GOP presidential nominee told voters during a Florida rally on Monday. Trump’s claim appears to be loosely based on a leaked 2008 email from a Democratic activist, which, as The Washington Post reported earlier Monday, includes an enjoinder to ‘oversample’ certain generally Democratic-leaning subgroups including racial minorities and younger voters…. Oversampling, though, isn’t about overstating the size of one group relative to others ― it’s about making sure the results for that group are as accurate as possible…. Since African-Americans make up about 13.6 percent of the population, for instance, a poll of 1,000 people would typically include only about 136 African-Americans. The margin of sampling error for African-Americans’ opinions in that case, per Pew, would be somewhere around 10.5 percentage points. So, pollsters interested in focusing on African-Americans’ views might oversample them as a group, conducting another couple of hundred interviews to bring up their sample size and lower the margin of error, offering more reliable information. The poll would still be weighted, however, so that African-Americans would account for the same 13.6 percent of the national population.” [HuffPost]

Most pollsters use oversampling - Andrew McGill: “Oversampling is... a completely valid statistical practice that everyone uses, including Republicans pollsters and probably Trump’s own campaign. If the polls are overestimating Clinton’s lead, and Trump is headed for an upset win, it’s not because of pollsters using oversampling to get more accurate results for demographic subgroups. ‘If you wanted to just bias the poll, you wouldn’t waste the extra money making all these extra calls—you’d try to manipulate it from the beginning,’ said Jon McHenry, a Republican pollster. ‘This is an added expense to the pollster with the idea of getting more information about a certain subgroup, and weighting that back so you understand the overall as well. Sometimes,’ he added wryly, ‘the polls say what they say because they’re accurate.’ It’s more common to complain about how pollsters weigh their surveys; The New York Times recently supplied four researchers with the same data and received five different results back, all because of differences in how the respondents were screened. Pollsters have different methods to determine whether a surveyed voter will actually cast a ballot, and that’s usually behind complaints about a given poll being too Clinton- or Trump-friendly.” [The Atlantic]

Debunking another polling myth: Polls didn’t miss badly on Brexit -

CLINTON IS GAINING AMONG YOUNG VOTERS - Laurie Kellman and Emily Swanson: “Liane Golightly has finally decided who she’ll vote for on Election Day. Hillary Clinton is not a choice the 30-year-old Republican would have predicted, nor one that excites her. But the former supporter of Ohio Gov. John Kasich says it’s the only choice she can make….Like Golightly, many young voters are coming over to Clinton in the closing stretch of the 2016 campaign, according to a new GenForward poll of Americans 18 to 30. Driving the shift are white voters, who were divided between the two candidates just a month ago and were more likely to support GOP nominee Mitt Romney than President Barack Obama in 2012. In the new GenForward survey, Clinton leads among all young whites 35 percent to 22 percent, and by a 2-to-1 margin among those who are likely to vote….Overall, Clinton leads Trump among young likely voters 60 percent to 19 percent, with 12 percent supporting Libertarian nominee Gary Johnson and 6 percent behind the Green Party’s Jill Stein. If Clinton and Trump receive that level of support on Election Day, Clinton would match Obama’s level of 2012 while Trump would fall short of Romney’s.” [AP]

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

-Americans are split on whether the country has changed for the better since 1950. [PRRI]

-Forty percent of Americans don’t think either Donald Trump or Hillary Clinton are funny. [ABC]

-Dylan Matthews compiles 21 charts and maps that help explain the election. [Vox]

-Only 7 percent of Republicans think their party is united now. [NBC]

-Many around the world say ordinary citizens can influence their government. [Pew]

-Fear of police runs high among black and Latino residents of the Washington, D.C. area. [American University]