Our poll is a good result for Republicans. It’s just one poll, though.

This survey was conducted by The New York Times Upshot and Siena College.

Hey, I’m Alex Burns, a politics correspondent for The Times. I’ll give you the latest reporting and intel on the midterms and take your questions from the campaign trail.

It’s generally best to look at a single poll in the context of other polls:

Mr. Chabot, 65, has represented the district almost continuously since 1995 (losing in 2008 but winning again in 2010) and has been a strong supporter of the Trump agenda, including voting to repeal the Affordable Care Act.

Unusually for a candidate challenging an entrenched incumbent, Mr. Pureval is leading in fund-raising as of the most recent reporting period, with about $1.6 million versus just under $1 million for Mr. Chabot.

Mr. Pureval, 36, an Ohio native of Tibetan and Indian descent, is a relative newcomer to politics, having been elected to the clerk of courts post in 2016. Before that, he worked as a lawyer.

This gerrymandered district includes most of the city of Cincinnati, and stretches out to conservative exurbs to ensure a Republican-lean.

is the current representative and a longtime holder of the office. 44% favorable rating; 38% unfavorable; 18% don’t know

But sampling error is not the only type of error in a poll.

One reason we’re doing these surveys live is so you can see the uncertainty for yourself.

As we reach more people, our poll will become more stable and the margin of sampling error will shrink. The changes in the timeline below reflect that sampling error, not real changes in the race.

Our turnout model There’s a big question on top of the standard margin of error in a poll: Who is going to vote? It’s a particularly challenging question this year, since special elections have shown Democrats voting in large numbers. To estimate the likely electorate, we combine what people say about how likely they are to vote with information about how often they have voted in the past. In previous races, this approach has been more accurate than simply taking people at their word. But there are many other ways to do it. Our poll under different turnout scenarios Who will vote? Est. turnout Our poll result The types of people who voted in 2014 201k Chabot +15 Our estimate 249k Chabot +9 People whose voting history suggests they will vote, regardless of what they say 252k Chabot +10 People who say they will vote, adjusted for past levels of truthfulness 263k Chabot +10 People who say they are almost certain to vote, and no one else 266k Even The types of people who voted in 2016 344k Chabot +8 Every active registered voter 468k Chabot +5 Just because one candidate leads in all of these different turnout scenarios doesn’t mean much by itself. They don’t represent the full range of possible turnout scenarios, let alone the full range of possible election results.

The types of people we reached Even if we got turnout exactly right, the margin of error wouldn’t capture all of the error in a poll. The simplest version assumes we have a perfect random sample of the voting population. We do not. People who respond to surveys are almost always too old, too white, too educated and too politically engaged to accurately represent everyone. How successful we were in reaching different kinds of voters Called Inter-

viewed Success

rate Our

respon­ses Goal 18 to 29 5 1 1 6 3 2 1 in 160 6% 10% 30 to 64 2 2 2 9 5 3 1 7 1 in 70 63% 59% 65 and older 7 0 2 2 1 5 4 1 in 46 31% 30% Male 1 6 1 9 3 2 2 8 1 in 71 45% 47% Female 1 8 2 5 5 2 7 5 1 in 66 55% 53% White 2 4 9 2 8 3 6 0 1 in 69 72% 71% Nonwhite 6 5 2 2 1 0 6 1 in 62 21% 20% Cell 2 2 9 8 0 2 6 7 1 in 86 53% — Landline 1 1 4 6 8 2 3 6 1 in 49 47% — Pollsters compensate by giving more weight to respondents from under-represented groups. Here, we’re weighting by age, primary vote, gender, likelihood of voting, race, education and region, mainly using data from voting records files compiled by L2, a nonpartisan voter file vendor. But weighting works only if you weight by the right categories and you know what the composition of the electorate will be. In 2016, many pollsters didn’t weight by education and overestimated Hillary Clinton’s standing as a result. Here are other common ways to weight a poll: Our poll under different weighting schemes Our poll result Weight using census data instead of voting records, like most public polls Chabot +6 Don’t weight by education, like many polls in 2016 Chabot +8 Don’t weight by primary vote, like most public polls Chabot +9 Our estimate Chabot +9 Just because one candidate leads in all of these different weighting scenarios doesn’t mean much by itself. They don’t represent the full range of possible weighting scenarios, let alone the full range of possible election results.