Centrist Democrats are forcing congressional leaders to moderate the majority’s liberal agenda, delaying a spending package and altering mortgage relief legislation.

New Democrats, ascendant during the Clinton administration, largely support President Obama’s job creation strategy: upgrades in the nation’s electric-power grid, better schools, incentives for “green jobs” and expansion of renewable energy. But the group is willing to slow other Democratic priorities.

“We’re Democrats. We will stand for small businesses and little people. But we’ll do it in a way that keeps in mind how the economy works and how capitalism works,” said Rep. Dan Maffei , D-N.Y.

The group flexed its muscle on March 5 when Sen. Evan Bayh , D-Ind., and other New Democrats balked at supporting the $410 billion omnibus spending bill (HR 1105), which would fund the government through fiscal 2009, and forced Senate Democratic leaders to delay a vote on the legislation.

In the end, Democratic leaders hope to win support for the spending package from the wayward Democrats, as well as Republicans such as Olympia J. Snowe and Susan Collins , both of Maine, by allowing Republicans to offer and debate additional amendments.

On the House side, the 67-member New Democrat Coalition is slated to hold its first meeting with Obama on Tuesday. Among their goals that may come up in the meeting: reviving stalled free-trade deals with Panama and South Korea, promoting market-based measures aimed at curbing the growth of health care costs and finding middle ground on mandates to cut carbon emissions.

Obama has offered mixed signals about whether he is willing to back the group’s positions over the more liberal positions of Democratic leaders.

In upcoming legislative showdowns, New Democrats may wield the balance of power on several Obama priorities: a health care overhaul, a cap-and-trade system for carbon emissions, and a $3.6 trillion budget, as well as the reauthorization of the 2001 No Child Left Behind law (PL 107-110).

The group counts former President Bill Clinton, former Vice President Al Gore and Sen. Joseph I. Lieberman , I-Conn., among its charter members. Its agenda has grown to embrace an array of policies that spur growth in quickly expanding industries, do not always hew to the demands of labor and stress issues important to suburban voters rather than those in inner cities.

“We want the right policy balance. . . . We want to make sure things are done a practical way. It’s going to take all of us working together to get to 60 votes to make things happen,” Bayh said.

With that in mind, Bayh convened a meeting of about 15 Democratic centrists last week to plot their strategy. They hope to extend a string of recent triumphs, such as the success of self-described New Democrat Sen. Ben Nelson of Nebraska and Collins to slice $108 billion from the $787 billion economic stimulus package (PL 111-5).

In the Senate, the loose coalition includes a half-dozen freshmen such as Mark Udall of Colorado, Mark Begich of Alaska, Jeanne Shaheen of New Hampshire and several Democrats elected in 2006, including Claire McCaskill of Missouri.

The group is often led by veteran New Democrats such as Bayh, Thomas R. Carper of Delaware, Mary L. Landrieu of Louisiana and Blanche Lincoln of Arkansas.