Lindsay Graham, John Kasich, Ted Cruz, Jeb Bush and maybe Rand Paul. The rest either endorsed Trump openly (Christie, Huckabee, Carson), chose to stay silent (I think) or at least tacitly endorsed Trump like Scott Walker and Rubio did, who more or less said "well, he's the guy now; you don't have a better choice so vote for him".
Thanks for reminding me that there are at least SIX of the Republican candidates for President 2016 who have lied and betrayed their written pledges to support the party’s nominee. TC is not the only candidate to betray his word, his trust, his sacred honor.