Alex Knepper, writing in the New American Perspective, thinks so:
A relatively strong Iowa finish by Rubio, a relatively strong New Hampshire finish by Kasich, and a relatively strong South Carolina finish by Bush all amount to this: Donald Trump steamrolling the competition. (As for Ted Cruz, he is likely to meet the same fate as the last two ‘winners’ of Iowa.) . . .
One week ago, I endorsed the conventional wisdom that we had a three-man race on our hands. The race is now effectively over. Let’s be blunt: Rubio had his shot to consolidate the center-right against Trump, and he blew it. Some will be tempted to blame Christie for spoiling a beautiful opportunity, but we should really be thanking him for doing us the favor of quickly exposing Rubio for the empty suit he’s always been. . . .
Given these dynamics, Trump is probably unstoppable. He is dominating the polls in every state that will vote over the next month, and he will only gain momentum from New Hampshire.
Sahil Kapur of Bloomberg observes:
Republican elites are 0-for-2 in presidential nominating contests this year, a rare and panic-inducing outcome for the party's leadership. Yet their preferred candidates continue to fight each other, and have begun the march to the next battlefield in South Carolina without a plan to stop Donald Trump. . . .
“Enormous pressure is on the establishment wing to consolidate around one candidate soon or else it will hand the Republican nomination over to Trump,” said Ron Bonjean, a Republican strategist and former senior congressional aide.
They're running out of time. With plenty of campaign cash to spare, Trump is pushing the kind of nationalistic message on immigration and foreign policy that resonates in South Carolina, a state that flew the Confederate flag on its capitol grounds until last year. The primaries beyond are just as southern and just as friendly to Trump's message.