No Republican has ever won the presidency without winning Ohio, the state hosting the GOP convention here.
So on the first day of the Republican convention, the Trump campaign, well, picked a fight with Ohio's governor. And the state party fought back -- all highlighting the GOP disunity in Cleveland.
When asked on MSNBC's "Morning Joe" about Ohio Gov. John Kasich skipping the GOP convention in his own state, the Trump campaign's Paul Manafort said, "He is making a big mistake. He is looking at something that is not going to happen. He is hurting his state. He is embarrassing his state, frankly." Manafort told the Today show the same thing.
And he made a third dig at a breakfast sponsored by Bloomberg: "That's a dumb, dumb, thing," Manafort said. "Will John Kasich finally grow up? Maybe. If he does, we'll welcome him."
Kasich is no ordinary governor. He was one of Trump's opponents during the 2016 Republican primary season, winning only his home state of Ohio. Kasich also has a 58 percent approval rating in Buckeye State, according a recent Quinnipiac poll.
And state Republicans, who haven't received prime seating at the convention despite their state's importance as a battleground state, fired back at Manafort.
"Ohio loves our governor. He turned this state around and united Ohioans. No wonder he has a 60% approval rating," tweeted Ohio Republican Party Chair Matt Borges.
This Kasich-vs.-Team Trump spat is only the latest sign of disunity at this Republican convention.
In the most recent NBC/WSJ poll, only 38 percent of Republican voters say they are satisfied with Trump as their nominee, versus 54 percent of Democrats who say they are satisfied with Clinton. What's more, a combined 85 percent of all voters -- including 78 percent of Republicans -- say the GOP is not that unified or only somewhat unified. That's compared with 48 percent of all voters (and 40 percent of Democrats) who say that about the Democratic Party.