Another problem with modern polling is that it isn’t, well, modern. Polls are still largely conducted using landlines, and people—especially in America—are increasingly turning to cell phones.

All this takes a toll on the reliability of 2016 polls, as Politico’s Steven Shepard wrote in 2014.

“As Americans become even harder to reach by phone—and emerging methodologies, such as Internet polling, remain unproven—the poor performance of pollsters this year casts serious doubt on the reliability of surveys during the 2016 presidential race,” he wrote.

So what are we to make of current polls? Certainly, reporting on where a candidate is polling can have an effect on the electorate, either by exciting or suppressing voters or forcing a candidate to make changes to their campaign. After several weeks of bad polls showing Democratic presidential nominee Hillary Clinton down to GOP nominee Donald Trump, the polls have shifted. Clinton is again leading Trump, after weeks of bad news coverage of the GOP nominee and the general consensus that Clinton won the first debate.