And on Friday, Sen. Lindsey Graham (R-SC) said he wouldn't vote for either Trump or Hillary Clinton.
Both George H. W. Bush and George W. Bush plan to skip the GOP convention in Cleveland and said they won't endorse Trump for president. And 2012 Republican nominee Mitt Romney said he won't be attending the Cleveland convention or voting for Trump, either.
House Speaker Paul Ryan appeared on CNN Thursday and said that he's not ready "at this point" to support Trump as the GOP nominee.
Former presidents and presidential candidates aside, for the Republican Speaker of the House not to endorse his party's candidate is a huge blow to Trump and the GOP.
Here's what former House Speaker and Republican presidential candidate Newt Gingrich said about Paul Ryan's dissension.
In a scathing article reacting to Trump's presumptive nomination, National Review writer David French said that it's "absolutely vital that conservatives stay firm in their opposition to Trump."
He also said that "Trump is the destroyer of conservatism, and he will taint all who take his side."
The Weekly Standard, another conservative publication, has also said it won't support Trump. Although, one of the Weekly Standard's most vocal Trump critics, editor Bill Kristol, said "never say never" when asked whether he'd support Trump in May.
The National Review and the Weekly Standard were instrumental parts of the #NeverTrump movement, which is still active in opposing the front-runner, even after his presumptive nomination. So far, the campaign has spent $75.7 million on over 60,000 negative ads to take down Trump.
While it's clear many in the GOP establishment are strongly against Trump, a few prominent others have taken a more conciliatory stance…
Some GOP Establishment Figures Urge Cohesion
GOP Chairman Reince Priebus tweeted shortly after Trump's primary victory in Indiana, urging Republicans to rally behind the billionaire.
Other notable GOP figures, like Sen. Jeff Sessions (R-AL), have criticized GOP establishment lawmakers for not getting behind Trump's candidacy.
On Thursday, Sessions said on the FOX Business Network that Paul Ryan's hesitation to support Trump "was a big mistake."
Sessions said that he's trying to talk with anti-Trump GOP leaders in Washington about overcoming their reservations about Trump.
Who's Afraid of Donald Trump? A powerful group of men joined together on Jekyll Island. Their goal was to secretly work their influence over the American people. And to stop the progress of Donald Trump's presidential campaign… at all costs…
- National Review: What Now, Conservatives?
- MSNBC: Meet the Republicans Speaking Out Against Trump
- eHeadlines.com: Is the GOP Out to Sabotage Donald Trump?