Hillary Rodham Clinton's presidential campaign suffered an embarrassing defection Thursday when former Democratic National Committee Chairman Joe Andrew, a superdelegate, switched his support from her to Barack Obama, warning other party leaders that the negative tone of the prolonged campaign was becoming a "catastrophe" that would help Republicans.
The announcement by Andrew, a former Indiana party chairman chosen by President Clinton to head the national party in 1999, was aimed at urging voters in his home state -- as well as the party's uncommitted superdelegates -- to rally around Obama and prevent further battling over the nomination that he said only helped the presumptive GOP nominee, John McCain.
"While I was hopeful that a long, contested primary season would invigorate our party, the polls show that the tone and temperature of the race is now hurting us," Andrew wrote in a lengthy letter released by the Obama campaign.
"John McCain, without doing much of anything, is now competitive against both of our remaining candidates. We are doing his work for him and distracting Americans from the issues that really affect all of our lives," Andrew wrote.
Andrew's home state of Indiana will, along with North Carolina, hold the next round of presidential primary contests Tuesday.
The decision by the longtime Clinton loyalist makes Andrew a leading voice among top Democrats who have expressed fears that the longer the campaign continues, the more divisive it will become. They worry that backers of each candidate will grow more hardened in their support and less likely to vote for the other.
"Should this race continue after Indiana and North Carolina, it will inevitably become more negative," Andrew wrote. "The polls already show the supporters for both candidates becoming more strident in their positions and more locked into their support. Continuing on this path would be a catastrophe."
Andrew had endorsed Clinton in November.
At a news conference Thursday, Andrew said Clinton's support for a federal gas-tax holiday over the summer was symbolic of a poll-driven candidacy proposing something "politically expedient to give a quick pander to Hoosier voters," in contrast to what he called the "principled" campaign Obama has run.
Obama has labeled as a "gimmick" a summertime suspension of federal gas taxes, which McCain also supports, and said it would provide little relief to motorists and would not wean the nation off of foreign oil.
Clinton's campaign rejected Andrew's contention that the continued battle was damaging the party.
"We just couldn't disagree with that more, and more importantly voters couldn't disagree with that more, given the fact that this process has attracted a record number of voters into the Democratic Party primary process," said Clinton spokesman Howard Wolfson.
Tribune correspondent Mike Dorning contributed to this report.