WASHINGTON — Republican challenger Stewart Mills has a slight cash-on-hand advantage over U.S. Rep. Rick Nolan, the man he’s trying to replace in Minnesota’s 8th District.

Nolan, a Democrat, had $298,000 in the bank at the end of December after raising less than $145,000 during the last three months of 2013, according to a Friday filing with the Federal Elections Commission. Mills reported $305,000 on hand, and he outraised Nolan for the second straight quarter.

At this point, Nolan is the only U.S. House incumbent without a cash-on-hand advantage over his opponent. He also had the weakest fourth quarter of any Minnesotan facing a serious re-election challenge — only Rep. Betty McCollum in DFL stronghold St. Paul raised less ($93,000).

Nolan’s weak quarter — and subsequent cash on hand shortfall — is certain to bolster Republicans, both in Minnesota and nationally, who have hoped to make Nolan a target this fall. Mills is a highly-touted recruit for the National Republican Congressional Committee, and conservative group Americans for Prosperity has already waded into the race, spending $225,000 on a December ad buy against Nolan.

His campaign sent a fundraising request to supporters on Thursday night raising the threat of future attacks from outside groups.

“Smart campaigns don’t wait around and let the other side’s attacks take hold with voters,” the note said. “They fight back.”

Devin Henry can be reached at dhenry@minnpost.com.