WASHINGTON – Barack Obama‘s recent rightward lurch on key issues is causing a revolt among left-wing bloggers and activists, who had been his earliest and most ardent supporters.

“Obama’s not just moving to the center for the general [election], he’s practically denouncing and rejecting every progressive voice in the country,” fumes Danner Kline, who blogs in Alabama for his Web site, 9Numbers.com.

Over the past several weeks, Obama has shifted from his liberal positions on gun rights, capital punishment and terrorist surveillance. And he walked away from his pledge to work within the confines of public campaign financing.

In addition, liberals lament, Obama took swipes this week at MoveOn.org and retired Gen. Wesley Clark for their fierce partisan attacks.

Just yesterday, Obama pledged support for expanding President Bush’s church-based federal assistance program, which is opposed by so many on the left.

When he first attended an Obama event a year ago, Kline said he was “awed” by an inspirational speaker who wouldn’t back down from his principles.

But then came Obama’s rotations.

“I have been staunchly in support of Obama until the past few weeks,” Kline told The Post.

While it’s still hard for him to imagine voting against Obama in November, Kline is shelving his plans to volunteer for his campaign.

“The way I’m feeling now, that’s not going to happen,” Kline said.

Kline’s discontent is being echoed across the very same liberal blogosphere that launched Obama from obscurity more than a year ago.

So much so that thousands of dissatisfied supporters have created a group on his Web site to protest his latest position on terrorist surveillance legislation, known as FISA.

Obama’s waffling on the issue is so incendiary among his supporters that some 7,000 have joined, according to one of the group’s organizers, making it the fourth-largest group on Obama’s Web site.

Blogger Greg Sargent, at TalkingPointsMemo, said what is so “dispiriting” for liberals about the vacillation on FISA is that Obama’s campaign is based on the premise that Democrats can go toe-to-toe with Republicans on national security issues.

But on this fight, Sargent said, Obama “abandoned that premise.”

Blogger Matt Stoller has gone from early Obama cheerleader to scorching critic in recent weeks, writing about the “corroded corruption at the heart of moving to the center.”

churt@nypost.com