Then there's Sen. John Boozman.
The 64-year-old Republican, facing re-election to a second term next year, has prompted growing concern from party elders who fear he risks a repeat of past election debacles -- where GOP candidates in Indiana, South Dakota, Kansas and Mississippi ran shoddy campaigns, forcing a last-ditch rescue attempt by the party establishment to try to save an endangered seat.
Senate Majority Leader Mitch McConnell has recently had a serious conversation with Boozman about the state of his campaign, sources said, and plans to headline fundraisers for the Arkansas Republican to help fill his coffers. The National Republican Senatorial Committee has also flatly warned Boozman that it will not spend a penny in Arkansas if he gets into trouble, according to several people familiar with the situation.
At a recent closed-door summit with party donors in Sea Island, Georgia, Ward Baker, the NRSC's executive director, didn't mince words about Boozman's campaign. While Baker said Boozman is a "good man," he added that his campaign has been slowly "trying to climb a mountain," according to two people present. The message was clear: Republican donors need to help fill Boozman's war chest.
The source of the concern stems from a well-funded Democratic opponent, Connor Eldridge, a former U.S. attorney for the Western District of Arkansas, who officially joined the race this week. Through September, Eldridge reported pulling in more than $403,000 through September -- outraising Boozman, who reported $359,000 in receipts in the last reporting period.
While Boozman still has more cash on-hand, the fact that Eldridge outraised a GOP incumbent and former 10-year veteran of the House prompted top Republicans to move.
In an interview with CNN, Boozman acknowledged his fundraising challenges, but said it wasn't due to inattention on his part. He said that donors weren't taking his race seriously and were instead funding more heavily contested seats in traditional battlegrounds. He said that he has been highly visible back home and has worked "really hard," dismissing chatter that he could be the 2016 version of Dick Lugar, the veteran Indiana Republican who lost in 2012 due in large part to a lackluster campaign.
"He's from a family of millionaires, so that makes a difference," Boozman said of Eldridge. "It's difficult though when you are an incumbent senator and most people don't feel you have a race."
Boozman said his conversations with McConnell and the NRSC have been productive.
"They certainly want me to have the resources that I need to run a good campaign," Boozman said. "Now that we have an opponent, we are working hard to raise the money that we need to get the message out."
Challenging national map for Republicans
For Republicans, the map is daunting heading into 2016, having to pump millions of dollars across the country in order to defend 24 seats compared to 10 for the Democrats.
Already, the GOP is at major risk of losing two seats -- one in Illinois and another in Wisconsin, and several more could also fall into Democratic hands, including in Pennsylvania, New Hampshire, Florida and Ohio. Only two Democratic seats are at risk of flipping -- Nevada and Colorado -- but Republicans have suffered recruiting failures in Colorado that make their chances of knocking off Democratic Sen. Michael Bennet increasingly difficult.
For those reasons, Republicans say that they cannot afford any surprises that would force them to squander precious resources -- something that has become all-too common in recent years.
In 2012, the party was unable to spare Lugar from losing to a tea party foe in his GOP primary -- only to see Democrat Joe Donnelly pull off a victory that November. And in 2014, problems with the lackluster campaigns of Thad Cochran of Mississippi, Pat Roberts of Kansas and Mike Rounds of South Dakota forced the GOP to spend millions to save seats in those red states. As a result, fewer resources could be spent in states where the GOP barely lost in 2014, including in Virginia.
For that reason, GOP leaders are trying to prod Boozman to step up now before it becomes too late.
"He is working hard to raise money," said Sen. Roger Wicker, chairman of the NRSC. "If he got off to a slow start, I think that is no longer the case."
Boozman's poor name recognition
As evidenced by Tuesday's elections, the South has grown increasingly red in the Obama era -- and Arkansas is no different. The era when Democratic giants like Bill Clinton and Dale Bumpers ruled the state is a thing of the past.
There are zero Democrats in the state's congressional delegation after Cotton trounced incumbent Mark Pryor by 17 points in 2014 -- just six years after Pryor skated in facing no Republican in the 2008 race.
Yet, Boozman is not a household name in Arkansas. A genial and soft-spoken pol, Boozman keeps a low-profile in Washington and doesn't seek the limelight back home. Last year, Boozman was sidelined for heart surgery to repair an aortic dissection, but he said he now feels "wonderful."
"It's better than I was before I got sick," Boozman said of his health.
Polls show that Boozman is not particularly well known. A poll released Wednesday from the University of Arkansas found that he had a 38% approval rating, with 44% of voters either didn't know him or refused to say how they felt.
Added to the challenge, the 38-year-old Eldridge, a former federal prosecutor who was confirmed to that post in 2010, comes from a wealthy family with interests in the banking sector and a tractor supply company.
Republicans have taken notice.
"If you are pointing out that his Democratic opponent -- an Obama-appointed, Democratic attorney -- is a multimillionaire, then you are making a very good point," Wicker said. "John Boozman is not a multimillionaire."
Brad Howard, a spokesman for Eldridge, said that despite the GOP gains in Arkansas, his boss is well-positioned in 2016, given that voters are fed up with Washington insiders.
"I think that this is a good election year to be an outsider," Howard said. "Folks just want someone new and strong and someone to shake things up."
Eldridge has not yet been endorsed by the Democratic Senatorial Campaign Committee, but national Democrats view his campaign positively and are likely to quickly get behind him.
But both sides acknowledge a Democratic victory in Arkansas would be one of the biggest upsets of the cycle -- and Republicans say Boozman has plenty of time to right the ship.
"My goal is to win with the same margin I had last time," Boozman said, referring to his 21-point victory over then-Democratic Sen. Blanche Lincoln. "I've had five terms in the House, and a term in the Senate, and my goal is that the committees will spend the same amount on me as they did the last six elections, which is zero."