Republican presidential candidate Jeb Bush laughs as he arrives for a campaign event at the Greasewood Flats Ranch in Carroll, Iowa, on Friday. (Rick Wilking/ REUTERS)

DUBUQUE, Iowa -- The $1.50 beer was flowing long before Jeb Bush got to the American Legion hall. This was the kind of place where his special guests, two Medal of Honor winners, got especially warm receptions. And it was, on this particular night, the kind of place where people were soused enough to tell him what they thought.

"Who made Osama bin Laden?" yelled a man wearing a Chicago Bears jacket, not waiting for Bush to call on him.

"Who... who made him?" Bush asked respectfully.

"The CIA did!" yelled the man.

"All righty," deadpanned Bush, as a beleaguered sheriff wound his way through the crowd to tell Chicago Bears Man to pipe down.

The raucous town hall meeting, which packed every inch of the venue, left some voters impressed with Bush's wit and "wonkish" obsessions. He walked them through the success of affirmative action reform in Florida, the details of his tax plan and what he'd learned as the brother of George W. Bush -- a name that drew immediate applause.

But it hardly resembled the closing rallies of Sen. Marco Rubio (R-Fla.) and Sen. Ted Cruz (R-Tex.), much less the airplane hangar-filling insult-fests of Donald Trump. And on Saturday afternoon, the final Des Moines Register/Bloomberg Politics poll of Iowa, widely considered the standard, found Bush at just 2 percent support, far behind Trump, Cruz and Rubio. One year, many campaign stops and $15 million of TV ads ago, the same poll had put Bush at 9 percent.

In a press scrum after the town hall, Bush brushed off questions about the bad numbers and pledged to worry only about what he could control. "If you want to elect someone because they’re popular, vote for Trump," said Bush. "He’d be an unmitigated disaster. I mean, vote for the winner because he’s winning? That’s the Trump attitude."

Yet it is Rubio, not Trump, who concerns the candidates trailing in Iowa. Every presidential candidate is confident that Trump's high unfavorable ratings would doom him in a two-way race. Rubio, who has withstood weeks of negative ads from the pro-Bush super PAC Right to Rise, threatens any chance that Bush, Gov. Chris Christie (R-N.J.), or Gov. John Kasich (R-N.H.) might have of forcing a battle with Trump. The punditocracy already seems primed to award a special ribbon to Rubio if he posts a strong third-place finish in Iowa -- something that could break him out of the four-way "establishment lane" tangle in New Hampshire.

That has effectively trapped Christie and Bush in Iowa, sending them from town hall to town hall to persuade voters not to bolt to Rubio. Neither is in the hunt for delegates here, but both stand to lose if the "narrative" -- as Bush disparagingly put it in Dubuque -- was of Rubio consolidating support. Sunday night, 24 hours before the vote, Christie will stump alongside Gov. Terry Branstad (R-Iowa), the closest that any candidate has come to a laying-on of hands from the state's Republican icon. Bush won't leave Iowa until Monday afternoon. Only Kasich has fled the state early, stumping in New Hampshire, a strategy that paid off for Sen. John McCain (R-Ariz.) in 2008.

"You fight for every vote," said Christie's campaign manager, Mike DuHaime. "I know John Kasich decided to leave, and that’s fine, that’s their strategy. But you have to respect the process."

Christie has fallen to 3 percent in the DMR/BP poll, ahead of Bush but only within the margin of error. And like Bush's, his town halls double as arguments against Rubio or Cruz. At a Saturday afternoon stop in Waterloo, Christie was introduced by Sen. Chuck Grassley (R-Iowa), then faux-apologized for what he was about to do.

"I'm going to say why those two first-term United States senators shouldn't be president of the United States, so hang in there," joked Christie. "If Marco Rubio just, like, looked into the camera, and said: 'Ladies and gentlemen, you saw that I had two different opinions there between 2010 and 2013. You know why? I had different opinions and I changed my mind.' Okay. Then what? What would be the follow-up question? 'You changed your mind?' Yes! Instead, they tried to hide it."

Christie spent almost seven minutes mocking the senators. Later, told a rose-colored version of how he left New Hampshire to guide his state's response to the January blizzard, and he mocked the idea of putting a "glib, teleprompter-reading" president in the White House to replace Barack Obama.

"That's the problem with politics in Washington," said Christie. "You've got too few people like Senator Grassley, who say what they think, and too many people like Senator Cruz and Senator Rubio who think, oh gosh, they can't be charged with flip-flopping. Well, with Cruz it would be flip-flopping, and with Marco it would be flip-flop-flipping."

If those critiques wound Rubio, no polling has shown it. The DMR/BP poll gave the Florida senator the second-highest favorable rating in the race, 70 percent. Bush and Christie were both underwater, with just 40 and 41 percent of Republicans viewing them favorably, and considerably more rejecting them.

So for the one-time "establishment" favorites, anecdotes are soothing the wounds left by data. Wherever Bush and Christie go, voters echo their message that first-term senators may be ill-suited to the presidency -- why, just look at who's in the White House.

"When you're 65, like me, you've seen life and you know what's ahead," said Bill Potulko, an Army Reserve veteran who caught Christie in Waterloo. "There's an expression -- senators don't make good presidents. And I think that might be true."

Bush, who has put real money behind his Rubio attacks, repeatedly asked his Dubuque audience to consider how inexperienced and political the senator was -- a man who would "cut and run" when the polls told him to.

"When the pressure mounts, you want to have someone who has a backbone to do what's right," said Bush. "Maybe it's okay to be 62 years old. At first I thought, you know, I always liked being the younger guy. Now I'm called the adult in the room."

As the din at the bar grew, 71-year old Curt Kaiser strained to hear Bush. Born in Oskaloosa, Iowa, he had moved to Florida, become a state legislator and come to admire the candidate enough to trek home and campaign for him.

"There've been 10 speakers of the House in Florida since we got term limits," said Kaiser. "Nine of them have endorsed Jeb. The tenth is Marco Rubio. That should tell you something."

Finally, a few hard drinkers who'd been cut off were pulled out of the venue. "I’ve been kicked out of better stuff than this," slurred one of them. The 200 or so voters remaining hung back to meet Bush, and the one-time favorite polling at 2 percent talked about the joyful campaign he'd bring to New Hampshire and South Carolina.

"Hey," laughed Bush, "if you can’t handle a guy with a couple of drinks in him, how can you handle being president?"

This story has been updated to correct Chris Christie's poll position.