INo good deed goes unpunished.

If Democrats take the House this fall, Minority Whip Steny Hoyer (D-Md.) will not be feted for the victory but will face a fratricidal challenge from Rep. John Murtha (D-Pa.) for the No. 2 post in the Democratic leadership.

It is no secret that the Pelosi and Hoyer families don’t vacation together. The frosty relationship between Hoyer and Minority Leader Nancy Pelosi (D-Calif.) is partly personal and partly political.

The personal differences are not hard to understand. Pelosi and Hoyer eyed a spot in the leadership for years, viewed each other as rivals and finally duked it out, with Pelosi prevailing. A contested leadership race almost always produces sore winners and losers.

Looking at voting patterns, the leaders’ political differences are apparent. Imagine a football field with House members laid out from left to right. Pelosi would stand around the 10-yard line and Hoyer at about the 30-yard line. Pelosi represents a very liberal San Francisco district that gave John Kerry 85 percent of the vote in 2004. Hoyer’s district includes a significant veteran and military population but is still solidly Democratic, having given Kerry 57 percent of its vote.

Those differences are real, but in the grand scheme of things not so great. Democrats once had a very conservative Southern wing, but Hoyer bears little resemblance to it and falls in the mainstream of his party.

But Hoyer’s support has come mostly from the more conservative members of the caucus: Blue Dogs, many of the 81 Democrats who supported the war in Iraq and Democrats closer to business interests. It is for this association that the liberal blogosphere has skewered Hoyer. If you have not had your daily dose of venom, google “Hoyer Murtha” and you will see how deeply the netroots community dislikes Hoyer.

It is into this already poisonous atmosphere that Murtha dropped his surprise announcement that he would challenge Hoyer if Democrats take the House. For most Americans, a congressional leadership race is the ultimate “inside baseball,” and thus the controversy will not have much effect on the midterm elections. But if Democrats do win the House, a bitter internecine battle can only hurt how they govern. Imagine if former Minority Leader Bob Michel (R-Ill.) had not decided to retire in 1994 and if Rep. Newt Gingrich (R-Ga.) had challenged him. Instead of a unified, energized team,  the early days of the Republican majority would have been marked by a bitter fight for the soul of the party.

And add to the Democrats’ problems that if they have a majority it will in all likelihood be by a minuscule margin. Again, not the ideal time for party strife.

The irony of the Murtha challenge is that, on paper, Murtha votes more conservatively than Hoyer. But Murtha’s calls for withdrawal from Iraq and his close alliance with the minority leader have made him the candidate of the Pelosi bloc.

So far, the Pelosi bloc has proved durable. Pelosi beat Hoyer 118-95. In the race for caucus vice chair, it became apparent that Pelosi candidate Jan Schakowsky could not beat Hoyer candidate Joe Crowley, so Pelosi and Murtha worked behind the scenes to throw votes to John Larson. Larson then beat Crowley 116-87 in the final round.

In a Murtha-Hoyer race, even if Pelosi remains formally neutral, there will be no doubt whom she supports. So if Democrats take the House and the Pelosi bloc unites, Democrats will celebrate their victory, have a bitter leadership fight and install a new leader. Will the sweetness of the return to power be salve for the self-inflicted wounds?

Fortier is a research fellow at the American Enterprise Institute.