Paul Singer, Influential Billionaire, Throws Support to Marco Rubio for President

Mr. Rubio has aggressively embraced the cause of wealthy pro-Israel donors like Mr. Adelson, whom the senator is said to call frequently, and Mr. Singer, who both serve on the board of the Republican Jewish Coalition, an umbrella group for Republican Jewish donors and officials. Mr. Bush has been less attentive, in the view of some of these donors: Last spring, he refused to freeze out his longtime family friend James A. Baker III, the former secretary of state, after Mr. Baker spoke at the conference of a liberal Jewish group.

The lobbying of Mr. Singer intensified in recent weeks as Mr. Bush’s debate stumbles and declining poll numbers drove many donors to consider Mr. Rubio anew. Last week, Mr. Bush’s campaign manager, Danny Diaz, and senior adviser, Sally Bradshaw, flew to New York to make personal appeals on Mr. Bush’s behalf, in the hopes of heading off an endorsement of Mr. Rubio, according to two people close to the former governor’s campaign.

.. Among Mr. Bush’s supporters after the debate, the tone was often one of despair, but it was rarely projected in public comments. Several of them said they took heart that Mr. Bush had acknowledged that he needed to be a more artful political performer in the weeks ahead.