face tough reelection congresswoman tammy duckworth vulnerable gop senator mark kirk illinois announce today un-endorsing republican presidential nominee donald trump tweet kirk say military experience help lead make decision give military experience donald trump temperament command military nuclear arsenal mark kirk markkirk june 2016then statement kirk tell reporters presidential campaign progress hop rhetoric would tone reflect campaign inclusive thoughtful principled oppose democratic nominee donald trump late statements context past attack hispanics women disable like make certain support party nominee president regardless political impact candidacy republican party like kirk become first republican un-endorse donald trump benn sasse lindsey graham republican senators nebraska south carolina pledge support trump either trump former rival senators ted cruz marco rubio still fence.other republican senators kelly ayotte bob corker mitch mcconnell susan collins jeff flake express condemnation trump comment judge preside university case pledge continue support.kirk announcement coincidentally come one day challenger duckworth say kirk refusal silence equal betrayal people.watch kirk explain reporters un-endorsement senatorkirk talk exclusively nbcnews halliejackson support trump pic.twitter.com/osxsmkwdt0 frank thorp frankthorp june 2016featured image via gabriella demczuk mark kirk become first republican un-endorse donald trump video