Downballot GOP candidates are more popular than Donald Trump. The national race is tightening a little, but the real question is whether Trump can catch Hillary Clinton in swing states. And pollsters mull the possibility of a reshaped electorate. This is HuffPollster for Friday, September 2, 2016.
MOST GOP SENATE CANDIDATES ARE OUTPERFORMING DONALD TRUMP - Republican candidates for Senate are seeing better margins against their Democratic opponent than Trump’s margins against Hillary Clinton in eight of the 12 states where HuffPost Pollster has sufficient polling data for a model, with incumbents Chuck Grassley in Iowa, Marco Rubio in Florida, and Rob Portman in Ohio holding the strongest relative numbers. Although Republicans are losing to Democrats on the generic ballot test, which asks voters which party they’d prefer to represent them in the House, they trail only by 4 points, as compared to Trump’s current 7-point deficit. The three exceptions to the rule are in Wisconsin, where incumbent Republican Ron Johnson is struggling in a rematch against Democratic former senator Russ Feingold, and in New York and Colorado, where the GOP is facing longshot battles against two Democratic incumbents.
Will voters split their tickets? - Ronald Brownstein: “Holding the Senate was always an uphill climb for Republicans this year because they are defending so many more seats than Democrats. But Donald Trump’s polarizing candidacy is converging with long-term shifts in voting patterns to make the hill even steeper. Since the 1970s, the share of voters who split their tickets—supporting one party for president and the other in Senate races—has steadily declined. If that pattern persists in November, Republicans will likely lose their slim upper-chamber majority because the most competitive Senate races are clustered in blue or purple states where Trump faces the greatest resistance. To maintain control, Republicans will need either a dramatic Trump recovery in states such as Illinois and Wisconsin—or to convince more voters to split their ballots in Senate races than either side has typically persuaded lately. Neither will be easy….If Trump can’t close the gap, Republicans will likely encourage more ticket splitting by explicitly urging voters to maintain a GOP Senate as a check on Clinton.” [Atlantic]
THE RACE FOR PRESIDENT IS TIGHTENING, BUT NOT THAT MUCH - Philip Bump: “Surrogates for the campaign of Donald Trump have been saying for several days that polls show a tighter race than shortly after the convention. It’s easy to pick out polls to make nearly any point, and paid advocates for campaigns are happy to do so. With that in mind (and new national polls from Fox News and Suffolk University in hand), we pulled poll and polling average data to figure out the extent to which that’s true…. Two charts here, the first of which simply shows all of the polls conducted over the past two months (that were included by Pollster). The second shows averages for those same three periods. Big jump for Clinton after the conventions — and a fade for Trump. But in the last two weeks, Trump again gained a point while Clinton slipped slightly. This is a modest change....The important question is if Trump can actually take the lead in the swing states.” [Washington Post]
Swing state polls seem to be following national trends - Nate Silver: “I’ve often heard Democrats express a belief that Clinton’s position in the swing states will protect her in the Electoral College even if the race draws to a dead heat overall. But this is potentially mistaken. Although it’s plausible that Clinton’s superior field operation will eventually pay dividends, so far her swing state results have ebbed and flowed with her national numbers. Take Wisconsin, for example. At her peak, Clinton had a double-digit lead there, according to our polls-only forecast. By Wednesday morning, it had declined to an estimated 7 points… At her post-convention peak, Clinton’s path of least resistance to 270 electoral votes appeared to run through a set of states that included Pennsylvania, Wisconsin and New Hampshire, among others. But in Pennsylvania, the most recent polls have Clinton ahead by margins ranging from 3 to 8 percentage points — perfectly fine, but not that different from her national numbers. We haven’t gotten much data recently from New Hampshire, but it can be swingy.” 
DID THE PARTY DECIDE? - Donald Trump’s nomination was a substantial departure from the usual party operation as described in a commonly cited political science book called “The Party Decides.” The basic theory articulated by professors Marty Cohen, David Karol, Hans Noel and John Zaller is that the Republican and Democratic parties usually act behind the scenes with money, endorsements and persuasion to choose the party’s presidential nominees. In 2016, Trump rose to the nomination despite widespread dislike among the Republican Party establishment, presenting a substantial challenge to the theory.
So what happened? There were three basic causes, Noel said Thursday on a panel at the American Political Science Association conference: First, the Republicans were already divided into factions, which Trump successfully leveraged to his advantage. Second, the “invisible primary” which usually takes place in the form of negotiations and endorsements among party leaders before voting begins, has become visible. And third, candidates have access to money earlier in the process than they used to. One setback doesn’t mean the theory is dead, though. As FiveThirtyEight’s Nate Silver, also a panelist, said, “I’d rather have a theory we can say is approximately right most of the time ― which this is ― than exactly right under only a precise set of conditions.”
THE POTENTIAL FOR TRUMP TO RESHAPE THE ELECTORATE CAUSES ISSUES FOR POLLING - Reid Wilson: “Pollsters are debating whether Donald Trump’s ‘silent majority’ of voters exists, and are scrambling to make sure that their surveys reflect the opinions of voters who might not ordinarily be included in opinion polls….‘We know some people who are traditionally seen as unlikely voters are going to vote,’ said Nick Gourevitch, a partner at Global Strategy Group, which polls for Democratic candidates….Modern public opinion polling is as much art as science. The science comes in measuring the attitudes of the American electorate, and key demographic groups, in a statistically valid way. The art comes in defining just what that electorate will look like, and how much of a percentage of the electorate key demographic groups will make up….’At some level, [voter models are] based on a hunch about the future and how it will resemble the past,’ said Ann Selzer, a nonpartisan pollster who conducts surveys for Bloomberg, the Des Moines Register and the Indianapolis Star. ‘The best predictor of future behavior is past behavior, until there is change.’” [The Hill]
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FRIDAY’S ‘OUTLIERS’ - Links to the best of news at the intersection of polling, politics and political data:
-Steven Shepard and Daniel Strauss report that Gary Johnson seems unlikely to make it into the presidential debates. [Politico]
-Most voters believe the U.S. is less safe than it was pre-9/11. [Fox]
-Harry Enten offers a list of tips for looking at election polls. 
-Drew DeSilver compiles 10 facts about American workers. [Pew]
-Americans still choose print books over e-books. [Pew]