Trump entered the Republican primaries on June 16 , 2015 , at a time when Governors Jeb Bush and Scott Walker and Senator Marco Rubio were viewed as the early frontrunners . Trump was considered a longshot to win the nomination , but his large media profile gave him a chance to spread his message and appear in the Republican debates . By the end of 2015 , Trump was leading the Republican field in national polls . At this point , some Republicans , such as former Mitt Romney adviser Alex Castellanos , called for a " negative ad blitz " against Trump and another former Romney aide founded Our Principles PAC to attack Trump . After Trump won the New Hampshire and South Carolina primaries , many Republican leaders called for the party to unite around a single leader to stop Trump 's nomination . The Never Trump movement gained momentum following Trump 's wins in the March 15 , 2016 , Super Tuesday primaries , including his victory over Senator Marco Rubio in Florida . After Senator Ted Cruz dropped out of the race following Trump 's primary victory in Indiana on May 3 , 2016 , Trump became the presumptive nominee while internal opposition to Trump remained as the process pivoted towards a general election . Following unsuccessful attempts by some delegates at the Republican National Convention to block his nomination , Trump became the Republican Party 's 2016 nominee for President on July 18 , 2016 . Some members of the Never Trump movement endorsed alternative candidates in the general election , such as Democratic nominee Hillary Clinton , Libertarian nominee Gary Johnson , independent conservative Evan McMullin and American Solidarity Party nominee Mike Maturen
Republican National Convention
2016 Republican National Convention
Stop Trump movement