May 1 (Bloomberg) -- Joe Andrew, a superdelegate and former Democratic National Committee chairman, switched his support to Barack Obama from Hillary Clinton and called on other top party officials to do likewise to unite the party.

Andrew, who earlier served as Indiana's Democratic Party chairman, said Obama is the best candidate to change the political process and the protracted nomination battle is making Democrats weaker in the general election.

``We cannot let our family affair hurt America,'' Andrew wrote in a letter to other superdelegates -- party officials and Democratic officeholders who will decide the nomination. ``It is clear that a vote for Hillary Clinton is a vote to continue this process, and a vote to continue this process is a vote that assists John McCain.''

The endorsement from Andrew, who was appointed Democratic chairman by former President Bill Clinton, is a boost for the Illinois senator, whose race with Clinton has tightened amid renewed scrutiny of his relationship with his former pastor, the Reverend Jeremiah Wright. Indiana and North Carolina hold primaries May 6.

``If we win Indiana, we've got this nomination,'' Obama said last night in Indianapolis.

Clinton dismissed concerns that the competition will harm the party's chances in the general election.

Good for the Party

``I think this has been good for the Democratic Party,'' she said in an interview recorded for ABC's ``Nightline'' program for broadcast tonight. Those making calls for her to concede the nomination and drop out of the race ``don't understand politics or history,'' she said.

The New York senator said the long campaign has generated enthusiasm from voters and is ``helping us build a stronger and deeper Democratic base.''

Clinton said Andrew didn't call her to tell her that he was switching to Obama.

Andrew said he was impressed that Obama hasn't partaken in ``political theater'' even as he has faced attacks over Wright.

He praised Obama for opposing a gas-tax moratorium that has been endorsed by both Clinton and McCain, the Arizona senator who is the presumptive Republican nominee. They have called for suspending the 18.4-cents-a-gallon federal gasoline tax this summer. Andrew said Clinton's alignment with McCain on the gas tax is a ``perfect example'' of typical Washington politics.

Matter of Principle

``It's also important to point out when someone is pandering and seeking political gain as opposed to standing up for principle,'' he said on a conference call with reporters.

Andrew endorsed Clinton on Nov. 8, citing her ``strength and experience to compete and win across this country,'' according to the announcement posted at the time on her campaign Web site. He served as Democratic chairman from 1999-2001.

``No amount of spin or sleight of hand can deny the fact that where there has been competition, Senator Obama has won more votes, more states and more delegates than any other candidate,'' Andrew wrote in his letter. ``Only the superdelegates can award the nomination to Senator Clinton, but to do so risks doing to our party in 2008 what Republicans did to our country in 2000.''

Other Endorsements

Clinton and Obama each picked up backing today from superdelegates who are also organized labor officials. Obama was endorsed by John Patrick, a Democratic National Committee member from Texas who is vice president of the AFL-CIO in the state. Clinton announced she is getting the support of John Olsen, a superdelegate who heads the AFL-CIO in Connecticut.

Clinton also picked up four so-called add-on delegates from her home state while Obama got three add-ons from Illinois.

Obama holds a lead in pledged delegates won in primaries and caucuses, 1,488 to 1,334, according to an unofficial count by the AP. Neither candidate is likely to secure enough pledged delegates to secure the 2,025 needed to win the nomination. That will leave it to the 795 superdelegates, about 290 of whom haven't declared who they will support.

Clinton leads Obama in superdelegate support, 260 to 247, according to lists provided by the campaigns and public announcements. Still, Obama has been closing the gap since the March 4 round of primaries.

To contact the reporters on this story: Julianna Goldman in Washington at jgoldman6@bloomberg.net; Nadine Elsibai in Washington at nelsibai@bloomberg.net

Last Updated: May 1, 2008 16:37 EDT