National Democrats are calling in reinforcements for U.S. Rep. Rick Nolan's re-election campaign in the Eighth Congressional District.

The Democratic Congressional Campaign Committee has added Nolan to its Frontline program — a support system for House Democrats' most vulnerable incumbents.

Nolan returned to Congress in 2013 after a 32-year hiatus, defeating a first-term GOP incumbent to win the seat representing northeastern Minnesota.

Republicans are looking to flip the seat once again, returning it to GOP control. Their candidate is Republican Stewart Mills III, a vice president in his family's Fleet Farm retail chain.

Mills has raised outraised Nolan in three of the last four fundraising cycles, but Nolan still holds an overall cash-on-hand advantage.

Mills has reached the top level of the National Republican Congressional Committee's "Young Guns" candidate training program. As challengers ascend the ranks, they're more likely to receive financial and campaign aid from the NRCC, the campaign arm of House Republicans.

The Rothenberg Political Report and Cook Political Report rate Nolan as a slight favorite to win re-election.

As Election Day nears, outside groups are expected to step up their spending in the race. In 2012, party committees and political action committees invested nearly $10 million in the Eighth District race. This year, conservative groups have already spent more than $500,000 backing Mills' campaign.

Nolan's assignment to the Frontline program will pair him with a familiar face: Fellow Minnesota U.S. Rep. Tim Walz chairs the initiative. As part of the effort, Nolan's campaign will have to ramp up its fundraising, volunteer recruitment and online networking.