WASHINGTON – When Rep. Rick Nolan walked the halls of the U.S. Capitol in 1978, the year of his last re-election campaign, his fellow congressman Tim Walz was a 14-year-old walking the halls of his high school in northwest Nebraska.

More than three decades later, Nolan is turning to Walz for advice on how to hold his new seat in Congress.

National Republicans have their sights set on Nolan's northeastern Minnesota district as a prime pickup opportunity this fall. The GOP is running a vigorous campaign aimed at casting Nolan as a dyed-in-the-wool liberal at odds with his blue-collar district.

Walz stared down similar challenges in 2008 and 2012 as the GOP made plays for his seat in southern Minnesota. His success led Democratic leaders to tap him as a mentor for their most endangered incumbents, including Nolan.

As chair of the Democratic Congressional Campaign Committee's Frontline Program, Walz is tasked with advising candidates on everything from fundraising to setting up get-out-the-vote efforts.

Since the program began in 2006, nearly 60 percent of its candidates have won. But the last midterm election was disastrous for the incumbent retention program.

In 2010, the midpoint of Obama's first term, Democrats lost 63 seats and control of the House. Thirty of the 39 Frontline Democrats lost that year — more than 80 percent.

Voters booted dozens of Democrats, regardless of whether they were liberals, moderates or conservatives, signaling their dissatisfaction with the status quo. Among the losers was the late Rep. Jim Oberstar, who had represented northern Minnesota for 18 terms. Republican Chip Cravaack defeated Oberstar, only to lose the seat to Nolan two years later.

While few political observers expect a repeat of the 2010 Republican wave this year, most political handicappers predict the GOP will add to its majority, and Nolan's seat is among those targeted.

The nonpartisan Cook Political Report rates Nolan's race with Republican Stewart Mills as a tossup.

Nolan declined to comment for this story.

The Frontline Program gives Nolan a fighting chance, said David Wasserman, who tracks congressional races for the Cook Political Report.

"The story from 2010 isn't that 80 percent of Frontline members lost," Wasserman said. "It's that Frontline helped 20 percent survive."

Defining a candidate

Nolan is one of 25 Frontline candidates this election cycle, but may be the one most familiar to Walz:

The Minnesota congressmen serve together on the House Transportation Committee. But Walz has been tight-lipped about any of his colleagues' re-election prospects. Campaign aides said Walz doesn't comment on specific candidates.

"He is … proud of the work he has done helping to identify and share best practices," said Walz's campaign spokesman Evan Peterson.

In placing Walz in charge, Democratic leaders said they are putting power in the hands of someone who knows how to survive tough races.

Nolan has certainly taken cues from Walz's playbook. In recent campaign ads, he's focused on veterans' issues, promoted his Second Amendment credentials and touted himself as a champion of the middle class.

"It's hard to argue with success, and Rep. Walz has run strong campaigns," said New York U.S. Rep. Steve Israel, chairman of the Democratic Congressional Campaign Committee.

Though Walz was a Frontline candidate just two years ago, he has not faced the onslaught of outside money flooding the Eighth.

Resources have rained in from both sides as Democrats and Republicans struggle for control of the swing district seat.

Democrats plan to spend at least $1.1 million on broadcast ads backing Nolan. To counterattack, the GOP has reserved roughly the same.

Soon after his return to Congress, Nolan condemned the frenzied pace of fundraising on Capitol Hill and the expectation to spend as much time dialing for dollars as he did legislating.

Now he's pushing to keep pace with Mills, who has outraised him in two of the past three fundraising quarters, a rarity for congressional challengers.

Nolan is "in one of the toughest battles in the entire country," Israel wrote in recent fundraising pitch to Democratic donors. "I'm not kidding when I say his race could come down to just a few votes."

Corey Mitchell is a correspondent in the Star Tribune Washington Bureau • Twitter: @C_C_Mitchell