Iowa's 3rd District ad buys near $13 million as fight for U.S. House intensifies

• Spending surpasses the state's other three districts, reflecting the race's competitiveness, according to Kedron Bardwell, a political science professor at Simpson College.

Catch up fast: The race is between Republican incumbent Rep. Zach Nunn and Democrat Lanon Baccam, an Army veteran and former USDA official.

State of play: Nunn, a former Iowa state senator and Air Force officer, ousted Democratic Rep. Cindy Axne two years ago by just over 2,000 votes.

• While Nunn has more name recognition than Baccam because of his time in the Iowa Legislature, he is still a freshman congressman and faces a "sophomore slump," when incumbents are often most vulnerable, Bardwell said.

Zoom in: Republicans could maintain control of the chamber if they win just 10 of the 23 seats considered tossups in the most recent ratings by the Cook Political Report.

• National Democrats had been eyeing the seat for months because they believe it could turn blue again.

Yes, but: The district has more active GOP voters, and Cook's report currently designates it as leaning Republican.

Follow the money: Democrats and their supporters have spent just under $6.8 million as of Friday, 17% more than the $5.7 million spent by Republicans, per AdImpact.

• Baccam's campaign has spent over $1.6 million on advertising, while Nunn's has spent just over $1 million.
• Congressional Leadership Fund, the primary super PAC for House GOP leadership, has spent just over $1.7 million.
• The House Majority PAC, House Democrats' primary super PAC, has spent $1.5 million.

Fun fact: Ad spending by both parties has more than doubled since mid-August, according to AdImpact.

The bottom line: The race is heating up.