Citing Senate races in West Virginia and Indiana in particular, Chris Wilson, a top Republican pollster, said evangelical turnout had picked up in recent primaries. Trump has taken steps popular among evangelicals in recent weeks, he noted, including pulling out of the Iran deal, moving the US embassy in Israel to Jerusalem and ending all taxpayer funding for clinics that provide abortion.

Other factors could push turnout the other way. In the 2017 Alabama Senate race, evangelicals made up a smaller percentage of the electorate than in the last comparable race for which there were exit polls, in 2012. They were far less likely to vote for the Republican, Roy Moore, than they had been for the Republican Mitt Romney for president. In the 2012 presidential contest, Romney received 90% of the white evangelical vote in Alabama. Moore got 80%. The judge, though, was, a divisive figure who faced allegations of sexually assaulting teenage girls.

Evangelicals have been less fazed by the constant drip of scandal around Trump, including his alleged sexual encounter with and hush payment to the adult film actor Stormy Daniels.