At 8 p.m. on Super Tuesday, things were looking up for Marco Rubio. In Virginia, he was winning by impressive margins in well-educated suburbs of Richmond and Washington, D.C. — much larger margins than he had achieved in places such as Charleston, South Carolina, and Des Moines, Iowa. Then his night spiraled downward in a hurry. Not only did he fall 3 percentage points short of Donald Trump in Virginia, but Rubio also just barely failed to clear 20 percent vote thresholds for winning delegates in Alabama, Texas and Vermont. With just 112 delegates, he now finds himself 124 delegates behind Ted Cruz and 226 delegates behind Donald Trump.

It’s fair to say that Rubio’s path to the 1,237 delegates required to clinch the Republican presidential nomination by June is probably shot. And although he has bigger problems ahead of him — namely finding a way to win his home state, Florida, on March 15 — nothing has cost him so dearly to date, apart from perhaps his New Hampshire debate gaffe, as the lingering candidacy of John Kasich.

Just how much has Kasich cost Rubio? The answer could be up to 91 delegates, even though Kasich has won just 27 so far and has a much less plausible path forward than Rubio.

As the two most mainstream Republicans remaining in the race, Rubio and Kasich draw similar profiles of support. Both rely heavily on well-educated Republicans in Democratic-leaning areas, and neither has performed as well in rural and working-class jurisdictions. There are important differences, too, beyond the fact that Rubio has garnered far more votes: Rubio has proven a hit with young and high-income suburbanites in the South, taking second place behind Trump in Georgia and Virginia. Kasich’s most reliable supporters have been older New England moderates, who powered him to second place behind Trump in New Hampshire, Massachusetts and Vermont. But it’s hard to deny their supporters’ overlap on the map:

But let’s pretend for a minute that Kasich’s votes went to Rubio in every primary. In this simulation, Rubio would have won three congressional districts in South Carolina (preventing a Trump sweep) and would have easily beaten Trump in Vermont and Virginia, shifting the narrative of the race. More importantly, Rubio would have easily cleared 20 percent thresholds required to win a significant number of delegates in Alabama, Texas and Vermont. Rubio would be holding 203 delegates, just five behind Cruz and 98 behind Trump — close enough for a Florida win to propel Rubio past Trump by a single delegate on March 15 (excluding other contests before and on that day).

In other words, the whole would be greater than the sum of its parts: Rubio’s 203 delegates would be 64 more than the 139 delegates Rubio and Kasich have tallied so far, even with the same overall number of votes.

ACTUAL DELEGATE COUNT RUBIO GETS KASICH’S VOTES STATE TRUMP CRUZ RUBIO KASICH TRUMP CRUZ RUBIO Iowa 7 8 7 1 8 7 7 New Hampshire 11 3 2 4 11 3 6 South Carolina 50 0 0 0 41 0 9 Nevada 14 6 7 1 14 6 8 Alabama 36 13 1 0 28 10 12 Alaska 11 12 5 0 11 11 6 Arkansas 16 15 9 0 15 12 13 Georgia 43 18 15 0 39 12 25 Massachusetts 22 4 8 8 22 4 16 Minnesota 8 13 17 0 8 12 18 Oklahoma 14 16 13 0 14 15 14 Tennessee 33 16 9 0 30 11 17 Texas 48 104 3 0 37 96 22 Vermont 8 0 0 8 6 0 10 Virginia 17 8 16 5 17 9 20 Total 338 236 112 27 301 208 203 What if Kasich’s votes had gone to Rubio? Source: The Green Papers

Of course, this is an extreme simulation, and in the real world of primaries, Kasich’s support would never transfer cleanly to Rubio. Nearly a month ago, before Jeb Bush and Ben Carson suspended their campaigns, an NBC News/SurveyMonkey poll found that Rubio was indeed the top second choice of Kasich supporters, but he was the second choice for only 24 percent of them. Another 21 percent went to Bush, 16 percent to Trump, 10 percent to Cruz and 6 percent to Carson. Now that Bush and Carson are out of the race, people who preferred one of them in the absence of Kasich would have to support a different candidate. If you redistributed those voters according to the second-choice preferences of those whose first choice was Bush or Carson, Rubio might top out at about a third of Kasich’s original supporters.

But even adding just a third of Kasich supporters would have made a huge difference for Rubio on Tuesday night: He might have won Virginia, hit the viability threshold in Vermont and beaten out Cruz for second place in far more Southern congressional districts, earning him dozens more delegates and changing the complexion of the race. Instead, Rubio is left to wonder “what if.”

Ironically, in the next crucial phase of primaries, Kasich’s relationship with Rubio may evolve from parasitic to symbiotic. After Trump’s Super Tuesday domination, Rubio’s and Cruz’s goals seem to have shifted from winning 1,237 delegates by the end of the primaries to preventing Trump from winning 1,237 delegates and forcing a contested convention in Cleveland. Kasich, who seems to be enjoying a much bigger home-state boost than Rubio relative to their national polling averages, may be the only candidate capable of preventing Trump from winning all 66 of Ohio’s winner-take-all delegates on March 15.

In short, Rubio badly needed Kasich out of the race about six weeks ago. But now, he may need him in the race more than ever.

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