“Marco’s in the driver’s seat. There’s a lot of disappointment in Bush’s performance,” said one Republican senator, who requested anonymity to discuss the race candidly.
The lawmaker, however, left the door ajar to the possibility of a Bush comeback, noting that “expectations for Jeb are so low that it won’t be hard to exceed them.

“He just needs a little momentum,” the lawmaker added.

Most GOP senators are waiting for the race to shake out before venturing to make a public endorsement, in case there’s a late reversal of fortune, which has happened in previous election cycles.

But one pro-Rubio senator said “it’s nearly unanimous” in the Republican conference that Bush is floundering and Rubio is on the rise.