Obama continued to gain support, picking up four superdelegates -- including former Clinton backers from North Carolina and Virginia -- as well as Inola Henry, a California member of the Democratic National Committee.
A more high-profile defector was George S. McGovern, the 1972 Democratic presidential nominee, who endorsed Clinton last fall at a campaign stop in Iowa. McGovern said Clinton had "run a valiant campaign" but stood no real chance of winning the nomination. But even as the former South Dakota senator endorsed Obama, he stopped short of urging Clinton to quit.
"Hillary, of course, will make the decision," McGovern told the Associated Press. "But I hope that she reaches that decision soon so that we can concentrate on a unified party capable of winning the White House next November."
Clinton politely brushed aside McGovern's comments, saying in West Virginia that "he has a right to make whatever decision he makes." She touted the support of Rep. Heath Shuler of North Carolina, a superdelegate who endorsed Clinton after she carried his district Tuesday.
In a further sign of her financial straits, Clinton sent an e-mail appeal for money Wednesday; she planned to attend a Los Angeles fundraiser next week. "As long as she is fighting, I'm going to fight on," said Sim Farar, a Los Angeles entrepreneur who has raised millions for Clinton.
Some major donors were offended when they received calls and e-mails from Obama backers urging them to abandon Clinton's campaign.
"The fact is, this is a marathon. She should be able to finish," said Eleni Tsakopoulos-Kounalakis, who is among Clinton's top Northern California fundraisers.
At this stage, the presidential campaign has become largely a matter of metrics, and Obama made gains Wednesday in two of the most important measurements: the number of pledged delegates and the popular votes cast in more than 40 contests nationwide.
Obama picked up at least 97 delegates in North Carolina and Indiana, according to the Associated Press. Under the party's proportional allocations, Clinton won at least 86.
That gives Obama 1,846.5 of the 2,025 delegates needed to win the nomination at the party's convention in Denver this summer. Clinton has 1,696 delegates, according to the AP.
Neither candidate can win solely with the support of pledged delegates, which has heightened the competition for superdelegates -- members of Congress and other party leaders who are automatically seated at the convention.
