Those summer town halls have provided lawmakers a first-hand glimpse of growing discontent among Americans over U.S. immigration policy. Seventy percent of Americans – including 86 percent of Republicans – believe undocumented immigrants threaten traditional U.S. beliefs and customs, according to a Reuters/Ipsos poll conducted in mid-July.

Those fears have been exacerbated by the recent wave of illegal child migrants from Central America. An issue that had been simmering is now hotting up as voters prepare to go to the polls in congressional elections due in November.

The anger and frustration expressed in the town halls suggests there will be a fierce debate when U.S. lawmakers return to Washington on Sept. 8 and take up proposals to address a flood of child migrants crossing the southwestern U.S. border.