In a sign that a presidential hopeful’s sexual orientation has diminished as a concern for voters, Americans are more likely to say they would reject a candidate older than 70 than a candidate who is gay, according to a Reuters/Ipsos poll on Monday.

The national opinion poll, conducted with the Williams Institute at UCLA ahead of the 50th anniversary of the Stonewall Uprising and the birth of the LGBT rights movement, highlighted a steady trend toward acceptance of gay politicians.

The survey also called attention to one of the challenges facing President Donald Trump, who will be turning 73 next week, as he seeks re-election in 2020...