Political betting markets and polls both give Democrats a big advantage in November, but it’s still early to predict what will happen. Americans with bleaker economic outlooks are more likely to support Trump. And AP-GfK is testing online exit polls. This is HuffPollster for Friday, March 18, 2016.

PREDICTION MARKETS FAVOR THE DEMOCRATIC NOMINEE IN NOVEMBER- David Rothschild: “The 10 March 15 primaries (five Democratic and five Republican) went just as expected, if you were following the prediction markets. On prediction markets around the world, people bought and sold contracts on any candidate winning...These contract prices are aggregated on my website, PredictWise.com, and turned into probabilities of any candidate winning any election….After Trump’s and Clinton’s strong showing on March 15, the markets predicted that the eventual Democratic nominee will win, at a probability of 72 percent….Here’s another point of reference. At this point in the 2012 presidential race, Barack Obama running for reelection was valued at a 60 percent likelihood to win….For March 16 of an election year, 72 percent is a very high probability of winning.” [WashPost]

Not that different from what polls are showing - Polling on hypothetical general election matchups shows similar results: The Democratic candidate -- whether Hillary Clinton or Bernie Sanders -- polls ahead of the most likely Republican nominee, Donald Trump. Clinton leads Trump by 8 points in the HuffPost Pollster model and Sanders leads by 11 points. Both Democrats lead over Sen. Ted Cruz (Texas) as well, but by smaller margins. There hasn’t been much polling of Ohio Gov. John Kasich against the Democrats, but he is the only Republican candidate to lead. However, these polling matchups should be viewed with caution.. Candidates will face more scrutiny and criticism in the general election campaign, and voters will be paying more attention in the fall. At this point, the results are not predictive of what would happen in November.

ECONOMIC STRUGGLES HELP EXPLAIN TRUMP'S POPULARITY - John Sides: "[P]olitical scientist Phillip Converse….found that people’s opinions of the parties and candidates were often based on how well things were going in the country. ….These are exactly the kind of voters who are supporting Trump... 'Our country doesn’t win anymore' and 'Make America great again' are refrains that tell voters that times are bad….It’s not surprising, then, that Trump’s support is strongest among those who are struggling….YouGov/Economist polls show that Trump’s gains among Republicans were larger among those who reported that their personal finances had gotten worse, compared to those whose finances had gotten better. The gap is now roughly 20 percentage points….Trump did about 30 points better among those who, almost one year earlier, were the most dissatisfied with their situation, compared to those who were the most satisfied." [WashPost]

Americans have mixed opinions on candidates’ tax proposals - Frank Newport: "Almost two-thirds of Americans agree with the idea of closing loopholes and removing deductions ‘available to the very rich’...Overall, broad plans to cut taxes for all income levels (part of Trump's plan) and to reduce the current complex system to a simple 10% flat tax (Cruz's proposal) are by no means big winners...Trump's idea of simplifying the tax code into four brackets, rather than the current seven, receives about four times as much support as opposition -- 47% vs. 12% -- but 41% of Americans, the highest for any proposal tested, say they don't know enough about it to have an opinion." [Gallup]

AP RELEASES RESULTS OF ONLINE ELECTION POLL TESTS - Paul Colford: "With a $250,000 grant from the Knight Foundation , AP hired GfK Custom Research to conduct an experiment with online surveys during last fall’s general elections in Kentucky and Mississippi… AP wanted to know if the online methodology could provide accurate and timely estimates of candidate vote percentages in small states that are difficult to poll with traditional methods.The GfK survey had the correct winner in all seven statewide races polled in the two states, including the Kentucky governor’s race. Pre-election polls had predicted a win for Democrat Jack Conway, but he ended up losing to Republican Matt Bevin by almost 9 percentage points. The GfK online survey had Bevin winning by just under 5 points. Overall, the online poll had an average error of 3 percentage points on candidate estimates across seven statewide races….Online panel estimates of candidate vote percentages in the gubernatorial and senatorial races in each of those states proved to be much more accurate than exit poll estimates." [AP]

Building on earlier tests - More from Colford: “The surveys in Kentucky and Mississippi built on experiments GfK conducted for the AP in Georgia and Illinois during the 2014 general election. Online panel estimates of candidate vote percentages in the gubernatorial and senatorial races in each of those states proved to be much more accurate than exit poll estimates. In Georgia, for example, a combined exit poll of Election Day voters and a telephone poll of absentee/early voters had Democratic winners in three of the four races. The online panel estimates correctly predicted Republican wins in all three races.” [AP]

WHY CAMPAIGNS NEED TO TRUST POLLSTERS - David Mowery: Polling, we’re told, is now in a state of perpetual crisis….Why, then, do campaigns of all sizes and candidates at every level listen to what public and private polling has to say? Why are the top pollsters still renowned as gurus? The collective schizophrenia around polling can seem perplexing, but it’s actually fairly simple. Unlike man, all polls are not created equal....What I can say about getting accurate results ...is that to get good results you have to be willing to pay what might seem like astronomical amounts of money….You also have to be willing to keep your length down, your sample size up, and avoid split testing as much as possible….You have to define your objectives up front, and be willing to make hard decisions about what to test and what to leave out. That’s where trust in your pollster is key." [Campaigns and Elections]

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FRIDAY'S 'OUTLIERS' - Links to the best of news at the intersection of polling, politics and political data:

-Millennials don't really understand where their water supply comes from. [HuffPost]

-Harry Enten notes that there is no relation between primary voter turnout and general election turnout. [538]

-A readability analysis by Carnegie Mellon University finds that Donald Trump speaks at a lower grade level than other candidates. [PsyPost]

-Kyle Kondik highlights four things the Ohio primary results tell us. [Politico]

-Pew Research points out that it's difficult to say how religious Trump's evangelical supporters really are. [Pew]

-Florida International University finds that most Latinos in the United States would vote for Hillary Clinton over Donald Trump. [FIU]

-A quarter of Americans say it would be difficult to cover an unexpected expense of $1,000. [Marketplace]

-A survey says Singapore has the best airport in the world. [USAToday]