The liberals are devouring themselves. At least some see the lunatic fringe like Kucinich as an obstacle to the Democrats being able to take power in both Congress and the White House. Mainstream America does not identify with kooks like Kucinich.
You are completely wrong on this. They do not see the lunatic fringe as an obstacle as they agree with a vast majority of what the lunatic fringe wants.
What they want though is to keep the lunatic fringe silent and hidden because exposure of their mutually shared agenda is the problem and causes them to lose.