A Democratic superdelegate and former head of the party who served while Bill Clinton was president said Thursday he's changing his allegiance from Hillary Clinton to Barack Obama because of Obama's skill in handling the Rev. Jeremiah Wright controversy and his opposition to a proposed gas tax holiday.

Joe Andrew had originally endorsed Clinton on the day she declared her candidacy for the Democratic presidential nomination. While holding a conference call in support of Obama on Thursday, he encouraged other superdelegates to act quickly in making their choice.

He said he's now convinced that Obama represents the promise for a change in the way Washington will work.

"What I saw this past week as Barack Obama answered the questions about his former pastor and as Barack Obama took on the heavy and difficult task of doing what is right on an energy policy and environmental policy and not doing what is politically expedient in order to give a quick pander to Hoosier voters to say we ought to have a cut in the gas tax reconfirmed to me in my mind that it is time for change," Andrew said from his hometown of Indianapolis.

Andrew also issued a letter that he is sending to superdelegates that says he is switching his support because "a vote for Hillary Clinton is a vote to continue this process, and a vote to continue this process is a vote that assists (Republican) John McCain."

Asked for a response to Andrew's decision, Clinton spokesman Phil Singer said, "We support that Democratic process and think that every American should be able to weigh in and support the candidate of his or her own choosing."Andrew becomes the second superdelegate this week to say he has switched his support for Obama as a result of the Wright controversy.

Indiana. Rep. Baron Hill, who represents a crucial swing district in the state, endorsed Obama on Wednesday. Clinton has the backing of Indiana Sen. Evan Bayh, who has a vast organization in the state and has been campaigning aggressively with the former first lady.

Obama initially refused to denounce his former pastor, but did so this week after Wright said Obama is just posturing to distance himself from a world view that could damage his campaign.

"He has shown such mettle under fire," Andrew said in the interview. "The Jeremiah Wright controversy just reconfirmed for me, just as the gas tax controversy confirmed for me, that he is the right candidate for our party."

Andrew's decision -- and the announcement of Texas superdelegate and United Steelworkers member John Patrick -- puts Obama closer to closing Clinton's superdelegate lead. Clinton had a big advantage among superdelegates, many of whom like Andrews have ties to the Clintons and backed her candidacy early on. But most of the superdelegates taking sides recently have gone for Obama, who has won more state contests.

Obama now trails her by just 16 superdelegates, 247-263. This week, he picked up 11 superdelegates, including three add-on delegates named by the Illinois Democratic Party, while she netted three.

Superdelegates are nearly 800 elected leaders and Democratic Party officials who aren't bound by the outcome of state contests and can cast their ballot for any candidate at the national convention. They are especially valuable in this race since neither Clinton nor Obama can win enough pledged delegates to secure the nomination through state-by-state elections.

Obama now leads in the delegate count overall 1735 to 1597 for Clinton. A candidate needs 2,025 delegates to win the nomination. About 230 superdelegates remain undecided, and about 60 more will be selected at state party conventions and meetings throughout the spring.

Other party leaders are encouraging superdelegates to pick a side by late June to prevent the fight from going to the national convention in August. Andrews wrote in his letter that he is calling for "fellow superdelegates across the nation to heal the rift in our party and unite behind Barack Obama."

Obama and Clinton are running close in Indiana and both need a victory there -- Obama to help rebound from a loss to Clinton in Pennsylvania and to prove he can win Midwestern voters and Clinton so she can overcome Obama's lead in the race overall.

In North Carolina, which votes alongside Indiana on Tuesday, Obama has been leading by double digits, but recent polls taken since Wright's outspoken press tour began last Friday show Obama may have been damaged by the relationship. Clinton has closed the gap and even passed him in one poll in the Tar Heel State, according to RealClearPolitics..

The Associated Press contributed to this report.