Republicans opposed to President Trump are quietly preparing to support Democratic front-runner Joe Biden, backing that could materialize in the primary as he attempts to fend off a surging Elizabeth Warren. Some Republican operatives active in Never Trump circles are discussing what form support for Biden might take and the timing. Groups such as Stand Up Republic, co-founded by prominent Never Trump Republicans Evan McMullin and Mindy Finn, could target disaffected GOP voters in key micro-battlegrounds with finely tailored advertising in a bid to boost Biden in the Democratic primary. Biden, 76, is the most likely Democrat to receive measurable...