Redistricting headaches have caused the Democratic Congressional Campaign Committee to release a new list of Members in its incumbent retention Frontline program for the 2012 cycle.

Reps. Russ Carnahan (Mo.), Mark Critz (Pa.) and Gary Peters (Mich.) were removed over the year from the Frontline program because they are “in or potentially will be in” races against other Democratic incumbents, according to a DCCC source. All three states lost a seat in redistricting this cycle, forcing incumbents to campaign against each other.

Members were both added and gradually removed from the original March list as redrawn lines have become more certain, the source said.

Newly drawn lines in California, Georgia, Iowa and Ohio also put some other incumbents in more competitive races. The DCCC added Reps. John Barrow (Ga.), Lois Capps (Calif.), John Garamendi (Calif.), Dave Loebsack (Iowa) and Betty Sutton (Ohio) to the Frontline program.

“Make no mistake, this cycle Democrats are on offense across the country,” DCCC Chairman Steve Israel (N.Y.) said in a statement.

He described the Frontline program as “critical” to the committee’s “Drive for 25,” which is the name of the Democratic effort to regain control of the House.

Even with the new additions, the Frontline program has a smaller list than the previous cycle. The 63-seat Republican wave in 2010 swept away a number of Democrats in competitive races. As a result, this time around Democrats have fewer endangered House incumbents to defend.