If you click on the link in this entry's title, you can read a study that was done by a Washington Post reporter showing that Democrats in the House of Representatives are voting together about 94% of the time. The previous record was held by the Republicans during the first two years of Bubble-Boy's first term. Then the GOP members voted together about 90% of the time. What makes the Democrats' unity even more remarkable is that they don't have a president who is setting the agenda. It would seem much easier for Representatives to stick together when they are following one person's agenda.
Of course, you still read stories about how much in disarray Democrats are over the war. Such stories became common place when the Democrats were in the minority over the 12 years between 1994-2006. When you don't control the majority, it is much harder for party members to stay united.
If Republicans lose the White House in 2008 and stay in the minority in 2008, you will start to see Republicans splintering and not staying united. This will be especially true of Republicans from "blue" leaning areas. Depending on the result of the 2008 presidential election, such Republicans might come from Ohio. With redistricting on the horizon, a Democratic governor, and a Democratic president, Republican House members might want to show that they can work with Democrats.