Rep. Joseph Crowley has pledged to bring his energy and ambition to the business-friendly New Democrat Coalition when he becomes the centrist group's chairman on Thursday.

His ascension ends a long, awkward transition that began in March, when it became known that the previous chairwoman, Rep. Ellen Tauscher (Calif.), was leaving to become the Obama administration's lead arms-control negotiator. After behind-the-scenes maneuvering, Crowley (N.Y.) emerged as the choice of the coalition's leadership to succeed her.

Crowley will take over leadership of of a caucus that claims many members but is not as high-profile as its fellow centrist caucus, the Blue Dog Coalition.

That profile could change under Crowley, whose leadership ambitions are well-known. He lost...