MASSACHUSETTS

Messy family legal problems may sink incumbent Democratic Rep. John Tierney and help make former state legislator Richard Tisei the first House Republican from Massachusetts since 1996. Tisei would also be the first Republican in the House who was openly gay at the time of his election.

REPUBLICAN SEATS THAT COULD GO DEMOCRATIC

CALIFORNIA

Dan Lungren, a nine-term Republican from the Sacramento area, and Democrat Ami Bera are in another expensive House race. More than $6 million in outside money has poured into the district, much of it to Bera’s benefit. Some congressional handicappers have the race leaning Democratic.

FLORIDA

Rep. Allen West, a tea party favorite and one of two black Republicans in the House, is engaged in a nasty battle with challenger Patrick Murphy. The Democrat has attacked West’s interrogation methods from when he was in the Army. West dug up a Murphy arrest from when he was a 19-year-old college student, on suspicion of drunk and disorderly conduct. (The case later was dismissed.)

ILLINOIS

Incumbent Rep. Joe Walsh, another tea party favorite, found himself in a redrawn district, courtesy of the state’s Democratic-controlled legislature. He faces Tammy Duckworth, a double-amputee Iraq War veteran, who spoke at the Democratic National Convention. Recent polls in Chicago have shown Duckworth with leads of 10 to 14 points over Walsh.

MARYLAND

Roscoe Bartlett, an 86-year-old, 10-term conservative lawmaker, is having his toughest run in years in a redrawn Democratic-leaning district. He faces political newcomer John Delaney, a Maryland businessman.

NEW HAMPSHIRE

It’s not easy being an incumbent New Hampshire Republican, as Reps. Charles Bass and Frank Guinta are learning. Bass narrowly won an open seat in 2010, a seat that he once held for six terms. He’s locked in a rematch against Ann McLane Kuster. Speaking of rematches, Guinta is in a tough contest against former Rep. Carol Shea-Porter, who’s trying to recapture the seat she lost two years ago.