With national Republicans honing in on his northeastern Minnesota congressional seat, Democratic U.S. Rep. Rick Nolan's campaign ramped up its fundraising in the first quarter of 2014.

Through the end of March, Nolan held a roughly $119,000 cash advantage over his Republican opponent, Stewart Mills III. Nolan had $478,000 banked for his reelection run while Mills had almost $356,000 cash on hand, according to their respective campaigns.

In a rare feat for a congressional challenger, Mills had outraised Nolan in the final two fundraising quarters of 2013. But Nolan raked in nearly $266,000 in donations during the first quarter of 2014, outraising Mills by $62,000 during the period. It marked Nolan's most successful fundraising quarter.

Outside money from political action committees and issue advocacy groups will likely factor in the race. Such groups spent millions of dollars in the district in 2012 when Nolan ousted first-term congressman Chip Cravaack.

American Action Network, a conservative advocacy group led by former Minnesota Republican Sen. Norm Coleman, spent $50,000 on television ads this spring targeting Nolan.

Dating back to last summer, the National Republican Congressional Committee has run several campaign anti-Nolan ads in the Eighth Congressional District. The NRCC, the campaign apparatus of House Republicans, has named Mills as one of its most promising recruits for the 2014 election cycle.