Republican presidential nominee Mitt Romney’s operation isn’t the only campaign sensing a last-minute opportunity in Minnesota.

House Majority PAC, a Democratic super PAC, started airing spots in the Gopher State’s 2nd district this week to boost former state Rep. Mike Obermueller’s (D) bid to unseat Rep. John Kline (R).

It’s a district both party committees bypassed in their fall ad buys, spending big in the highly competitive 8th district instead. Roll Call rates the 2nd district as a Likely Republican seat.

HMP’s $65,000 buy in the Twin Cities market will air this spot on stem cell research:

The super PAC is also expanding existing buys for similar stem cell spots in other races: $150,000 in Minnesota’s 8th district, $150,000 in Colorado’s 6th district and $200,000 in California’s 7th district.