The GOP's newest candidate has its most fascinating history with Obamacare
His success or failure largely depends on whether his brand of moderation catches on with Republican primary voters. That includes the topic of Obamacare, with which Kasich has a complicated but much different history than almost all of his rivals.
Kasich is the only Republican governor - in a field with three other current or recent governors - to have expanded the federal Medicaid program under the Affordable Care Act. And because of that, he already has a big target on his back from conservative groups like the Club for Growth.
"John Kasich's decision to expand Medicaid in Ohio in 2013 was a costly mistake," Club for Growth President David McIntosh said in a statement Tuesday.
"Medicaid enrollment in Ohio has far outpaced Kasich's projections and more than doubled in cost. The Club for Growth is concluding its research into Kasich's broader record on issues of economic freedom. But, our presidential white paper on the Ohio governor will, no doubt, warn of the long-lasting consequences from his decision to burden Ohio with an ever-growing price tag for Medicaid expansion."
In many states including Ohio, Medicaid enrollment has exploded beyond projections, giving credence to Republican arguments that the state and federal governments would struggle to pay for such an expansion. More than 500,000 Ohioans have already been covered under the expansion.
Nevertheless, Kasich has been unusually blunt on the issue. He has taken the position, along with many other more moderate Republicans, that red states should expand the Medicaid program because it helps poorer individuals and families obtain health insurance - and because the federal government is picking up 100% of the costs through 2016 (and at least 90% after that).
Kasich's approach has been markedly different than former Florida Gov. Jeb Bush (R), for example, who reportedly lobbied Florida Republican lawmakers in 2013 to reject the expansion, even as Gov. Rick Scott (R) supported it at the time. Other presidential candidates - former Texas Gov. Rick Perry, Wisconsin Gov. Scott Walker, and Louisiana Gov. Bobby Jindal - have rejected the expansion.
Last year, Kasich caused a bit of a kerfuffle when he criticized opponents of the law and said a repeal of the law's Medicaid provision simply wasn't going to happen. He has continued to defend the Medicaid expansion over the past year, hitting on the "compassionate conservatism" that will likely become a theme of his campaign.
"First of all, I don't support Obamacare; I want to repeal it," Kasich told CNN recently. "But I did expand Medicaid because I was able to bring Ohio money back home to treat the mentally ill, the drug addicted and help the working poor get health care."
He has been similarly unapologetic to the Republican Party's donor class. Politico recounted an instance last year when Kasich, who was attending a conference hosted by the mega-donor Koch brothers. One donor criticized him for expanding Medicaid, and he reportedly did not hold back.
"I don't know about you, lady," he said to the donor. "But when I get to the pearly gates, I'm going to have an answer for what I've done for the poor."
Kasich's dealings with Obamacare have been a theme of his governorship - he's to the left of almost all GOP candidates on immigration, and he has embraced the Common Core educational standards.
But the Medicaid expansion will stick out - because it is still a litmus test for conservatives. When the Supreme Court saved a key provision of the law last month, every GOP candidate issued a statement pledging to repeal the law if they win the White House.
The big question: It remains to be seen if Kasich's pragmatic style fits with his party's now-rebellious nature. For now, he's polling at an average of just 1.5% in an average of recent national polls.