ST. PAUL, Minn. (AP) — A congressional rematch in northeastern Minnesota is testing whether Democrats can hang onto a seat they've held almost exclusively for decades.

Democratic Rep. Rick Nolan is on his heels again in a race against Republican challenger Stewart Mills. Nolan narrowly defeated Mills in 2014. Mills is the grandson of the founder of Mills Fleet Farm, which was recently sold by the family.

The race is the second-most expensive congressional contest in the country. At last report, more than $10-million had been spent in support of the two candidates.

Presidential voter turnout that generally favors Democrats should help Nolan, but the district has become more Republican over the years through redistricting and migration.

Mills calls it a tossup. He's targeting voters in the Duluth area to chip away at the support Nolan needs to win.

Democratic consultant and local blogger Aaron Brown says economic uncertainty also gives Mills and Republican presidential candidate Donald Trump a chance.