ASHBURN, Va. — It was a hot day outside at Ashby Ponds, a retirement community where Sen. Mark Warner was hosting a town hall Sunday, and once inside Warner wanted to take his suit jacket off. Would that be OK, he asked a man in the crowd?

The man, dressed in a jacket himself, acceded. “It might help you with the result up there,” he deadpanned.

“Does that mean you’re going to make me sweat on some of these questions?” Warner laughed.

He was only half-joking. Warner is running for re-election against Republican Ed Gillespie, and although Warner has been leading in public polling, Democratic candidates are facing a stormy outlook in the final stretch of the midterm elections. In an unscripted town-hall setting, Warner might have expected the worst.

At a moment when President Obama faces terminally low public approval, coupled with potentially controversial decisions on everything from foreign policy to immigration reform, Democratic candidates must face voters back home who want to talk about it.

The town hall has long been a mainstay of congressional recesses, when lawmakers update their constituents on their work in Washington. But some vulnerable Democrats running for re-election have calculated that, in this election cycle, the risks of the unscripted format outweigh the benefits.

In New Hampshire, Republican Scott Brown has attacked Sen. Jeanne Shaheen for not holding a town hall yet this year. Meanwhile, the state GOP has dispatched a chicken mascot to follow Shaheen to events, with a sign calling Shaheen “too chicken for town halls.”

Shaheen has instead turned to alternate forms of communication, like a tele-town hall. Sen. Mary Landrieu, a Democrat in a tight race for re-election in Louisiana, recently participated in a Google Hangout with constituents, but has steered clear of the town hall circuit.

In 2009, Obamacare-related confrontations at town hall meetings were the earliest signs of the voter angst that propelled a Republican wave in the 2010 midterm elections. This year, however, the health care law has not commanded nearly the same attention. Instead, other issues, such as immigration reform, have moved more to the forefront.

"We've had seven town halls, and immigration is the No. 1 issue that comes up," Rep. Jared Polis, a Colorado Democrat, recently told Reuters.

Immigration reform risks becoming an even more damaging issue for many vulnerable Democratic candidates, who fear the president could take sweeping executive action on immigration prior to November. Such action would likely elevate immigration as a political issue during political crunch time, immediately before the midterm elections.

In Ashburn, Warner came prepared to talk about veterans and student debt, but a few audience members steered the conversation to immigration reform. One man asked, why wouldn’t the Senate take up the border security bill passed in the House?

The House “just took a piece of border security, they didn’t take on any of the other aspects,” Warner reasoned. “To do a one-off like this, I guess the response I have is, why not take the comprehensive [bill] that the Senate passed and take out the parts they don’t like?”

Afterward, one woman speaking to her friends was not impressed with that response. “Sounded like a stock answer to me,” she said.

But, for all the challenges Democrats face, the explosive town halls of 2009 and 2010, this was not. Warner didn’t even break a sweat.