REUTERS/Gretchen Ertl
Jeb Bush with Lindsey Graham.
"If Rubio beats him badly in New Hampshire, Jeb is toast," Graham, who spent Tuesday campaigning with Bush, told The New York Times.
He added that Bush has to "tie Rubio or beat him" in New Hampshire, which holds the first-in-the-nation primary next Tuesday.
For his part, when pressed about whether he could stay in the race should he not perform that well in New Hampshire, Bush brushed the idea aside.
"Oh, I'm continuing on," he said, according to The Times. "I'm continuing on, yeah."
Bush's strategy is centered on a strong performance in New Hampshire. Most of the money Bush and his allied super PAC, which had $58.6 million in the bank as of January 1, has spent this election cycle has come in the Granite State. He has campaigned there with increasing frequency in recent weeks.
In Monday's Iowa caucuses, Bush received slightly less than 3% of the vote. Rubio, after a big surge in support during the last days before the caucuses, earned roughly 23% of the vote, nearly overtaking businessman Donald Trump for second place.
New Hampshire, however, is friendlier terrain for Bush. And he fares slightly better in New Hampshire polls, with his RealClearPolitics average in the state standing at 9%.
However, he is locked in a battle with not only Rubio, who he trails, but also other candidates Ohio Gov. John Kasich (R) and New Jersey Gov. Chris Christie (R). Bush's polling average is currently third among those four candidates, all of whom are vying to take control of the "establishment" lane.
If one of those candidates separates himself from the rest of the establishment pack, others could face pressure to leave the race to consolidate support and build a stronger challenge to Trump and Sen. Ted Cruz (R-Texas).