How could it be that Ohio Gov. John Kasich was the most important person at last night's Republican presidential debate?

According to the fast-forming conventional wisdom, the longshot candidate was one of the bigger losers of the debate. But his influence on the field, already outsized, hit a fresh high.

It was Kasich's entry in the race in the first place that complicated Sen. Marco Rubio's positioning relative to Jeb Bush. Back when Bush seemed formidable — if not inevitable — Kasich's crowding of the establishment side of the field posed a real problem for Rubio. With Bush's numbers still high and Kasich carving out a small but crucial slice of the primary electorate, the senator had to tilt right without looking like a fraud.

That took careful maneuvering, especially on immigration. But Rubio executed brilliantly. Instead of helping Bush dispatch Rubio, Kasich actually forced Rubio to elevate his game. Both men left Bush to his own fate — at first, out of political necessity. Then, however, Bush's struggle to capitalize on his advantages allowed both Rubio and Kasich to stand back as he became his own worst enemy.

That weird dynamic couldn't last forever, and it didn't. Chastened, Bush commenced with a campaign reboot, which demanded he set a stronger, surer tone at the debates. Alas, after Rubio shamed Bush onstage in October for a particularly feeble attack on his Senate attendance, last night was perhaps the beleaguered former Florida governor's last chance to show some spine.

And that's where Kasich came in, again.

Over the course of the debate, Kasich did not exactly distinguish himself — in the way his supporters might have hoped, anyway. Querulous, uneven, and sometimes downright snotty, he managed to wrap his often RINO-esque positions in the kind of exasperated contempt that plays poorly on television, especially to the older constituents who might as well slap on a bumper sticker reading, "I PRIZE SUNNY OPTIMISM — AND I VOTE!"

But none of that really mattered. With Chris Christie relegated to the undercard debate, Kasich had but one strategic objective yesterday night: to show Bush voters what a real fire in the belly looks like. Sure, he took it too far for rightwing populists, raining derision on Donald Trump and other immigration hawks. But in New Hampshire, which Bush is treating like a must-win, the Kasich we saw last night is likely to play much differently.

In a vacuum, that shouldn't be enough to knock Bush out of the race. But this primary campaign is anything but a vacuum. Bush is walking a razor-thin wire of expectations, and if he flames out in New Hampshire, finishing behind Kasich, his donors' departures will shift from a regretful trickle to a mortified stampede.

Suddenly the broader contest would shift from the two-lane dynamic Sen. Ted Cruz has been hyping — in order to cast himself as the conservative to Rubio's moderate — to a three-lane affair, with Rubio looking responsibly conservative, Kasich looking responsibly moderate, and Cruz stuck with Trump and Carson in the neither/nor category.

The Kasich we saw last night keeps the race fluid, crowded, and hard to game out. Republicans as a whole might be souring on their seasoned executive from must-win Ohio, but the man himself appears to think he's hitting his stride. With Bush falling another step behind, Kasich's confidence could make all the difference.