Nothing like a little red-on-red action to brighten your day.

(The Hill)– Liberal groups need to stay out of Democratic primaries if the party is going to retake the House majority, according to a conservative Massachusetts Democrat.

Rep. Stephen Lynch was one of several Democrats who faced an aggressive primary challenge from the left in 2010. His challenger Mac D’Alessandro, a former top official with the Service Employees International Union (SEIU), received almost $300,000 from labor groups for his campaign.

“There was a lot of money spent against Democrats by Democrats,” Lynch told The Ballot Box. “That contributed to the scale of our losses.”

Lynch survived his primary and was reelected in November, but several House Democrats who were targets of the left lost their reelection bids. For instance, the SEIU encouraged its members in Ohio’s 18th district to “skip-a-Space” on their ballots and not vote for Rep. Zack Space because of his opposition to healthcare reform. The two-term Democrat was subsequently defeated by Republican Bob Gibbs.

Liberal groups also targeted Alabama Democrat Bobby Bright because of his opposition to the healthcare reform bill. The group Blue America PAC spent almost $50,000 against Bright – in the general election, according to records compiled by the Sunlight Foundation, a nonprofit watchdog group.

And in New Hampshire, liberal groups helped Ann McLane Kuster defeat establishment-favorite Katrina Swett in a bruising 2nd district Democratic primary. Kuster went on to lose to Republican Charlie Bass in a tight vote.