I'm linking you here to an article entitled, "Democrats, Like Cheney, Are Shooting Their Own" that talks about this situation. Here's an excerpt:
Cheney can’t tell a quail from a Republican, which may be understandable from an intellectual point of view, but the Democratic Party’s killing off of progressive Congressional candidates is something more treacherous: suicide. Dick Cheney may have demonstrated his ability yet again to go after the wrong target when he bagged his hunting companion instead of his quarry, but the Democratic Party leadership is proving to be even more treacherous in the field than Deadeye Dick.
Party leaders, including Sen. Barbara Boxer (D-Calif.) recently pressured Cindy Sheehan not to mount a primary campaign against California Senator Diane Feinstein, a woman who has betrayed party principles, such as they are, at almost every turn and deserves to go down to defeat. (It was only after Sheehan said she was considering a primary fight that Feinstein announced she would support a filibuster on Alito.) Now they've killed the campaign of Paul Hackett, an Iraq War vet and sharp critic of the war and the president and a candidate who had a strong shot at snatching a Senate seat for the Democrats this fall in Ohio.
For months, the Democratic National Committee, and the Democratic Senate Campaign Committee chair, Sen. Charles Schumer (D-NY), have been working behind the scenes to undermine Hackett's campaign in favor of Rep. Sherrod Brown. When Hackett announced his intention to run, he met with party leaders, and with Ohio Rep. Sherrod Brown, and won a commitment from Brown not to enter into a primary fight for the Democratic senate nomination. Later, the party leadership undercut him and had Brown go back on his promise, forcing a primary battle. The undermining effort continued and Hackett finally decided Monday he didn't want the fight.
Saying he had been betrayed by his country when he was sent to Iraq, and now by his party, Hackett, a Marine reservist and a lawyer, said he was quitting politics in understandable disgust, but would continue to speak out against the war. I'm sorry he decided not to fight, but understand his disgust.
Only a few days ago, I received a call from a fund-raiser for the DNC asking me to help the party elect a Democratic Congress in 2006. I told the woman she was wasting her time, and that I would not give a penny to a corrupt and self-destructing organization that was so afraid to be a genuine opposition party that it would sabotage its own best candidates. She indignantly asked me who the DNC had sabotaged and I ran a whole list by her, from Cynthia McKinney to Cindy Sheehan. Now we can add Paul Hackett to the list.
Paul Hackett was a dream of a candidate. He ran an amazing race in heavily Republican territory against Jean Schmidt and made her fight for her life. He almost won and he was running against enormous odds.
To learn more about how the party screwed him over read the AP article "Iraq Vet Abandons Ohio Political Bid".