Biden had also planned on raising money for New Hampshire Gov. Maggie Hassan (D) last month but had to cancel after his son, Beau Biden, fell ill.
Biden has not ruled out a run for the White House in 2016, and news of him raising money for Democrats in the state will only fuel speculation.
Mowrer, an Army veteran, served a tour of duty in Iraq in 2005. In 2010, he worked as special assistant to the undersecretary of the Army. He worked for Biden's 2008 presidential campaign.
He is challenging six-term incumbent Rep. Steve King (R-Iowa).
King beat out Christie Vilsack — former Gov. Tom Vilsack’s wife — by 8 points in 2012. He won the majority of his early races with more than 60 percent of the vote. But redistricting drew him into more Democratic territory during the 2012 election.
King has created his own presidential speculation after visiting North Carolina earlier this year and confirming plans to speak in New Hampshire’s Strong New Hampshire Conference in October.
— An earlier version of this report stated that Vice President Joe Biden was hosting the fundraiser. This version was corrected at 4:00 p.m.