Donald Trump's call for 'shutdown' on Muslims entering US escalates GOP rhetoric on Islam

For months, Republican presidential candidates have steadily escalated their rhetoric about the place of Muslims in the United States.

A Muslim shouldn't be president. Muslims fleeing war-torn Syria and Iraq should be barred from the U.S. Mosques should be under surveillance and shut down if people are radicalized in the places of worship.

Republican front-runner Donald Trump's call Monday for a "total and complete shutdown of Muslims entering the United States" was the latest salvo for a party aggressively testing the boundaries between concerns about security and discrimination against a religious group.

For most of Trump's rivals in the 2016 race and numerous other Republicans, it was also the proposal that finally crossed that line.