Judy Woodruff:

And now a congressional race that could be a harbinger of elections to come this fall.

In 2018, President Trump won big in Pennsylvania's 18th Congressional District, outside of Pittsburgh, but polls ahead of tomorrow's special election there show the Republican, Rick Saccone, in a dead heat with Democrat Conor Lamb. It's an early and critical test of enthusiasm for both political parties.

Lisa Desjardins just returned from Western Pennsylvania and brings us this report.