By Richard Wolffe

Call it the Palin effect in reverse. John McCain’s veep pick isn’t just firing up the GOP base with bigger crowds and more cash. Sarah Palin is having the same impact on the progressive base of the Democratic Party.

Take a look at what’s happened to MoveOn.org, the signature online left-of-center group that marks its 10th anniversary this year. The group has added almost a million new members since 2007, many of them over the summer, to bring its total to 4.2 million – around the same size as the NRA on the right. Along with the new members, there has been a surge in donations allowing the group to double its advertising budget for the general election period to up to $7 million.

“We’ve seen an increase in energy, particularly driven by the tightening of the race, but also by I think McCain’s choice of Palin,” says Eli Pariser who directs MoveOn. “That really sunk in for people that this would be another Bush-style presidency, both in terms of the cynicism of the choice and what it says about his far-right views, that he would pick someone who has such extreme views on choice and creationism for instance.”

While MoveOn spent millions on ads in 2004, this time around its spending has been pushed later in the cycle. Its ads are also responding to the rapidly shifting news cycle of the campaign: its latest commercial, attacking McCain for his ties to lobbyists, tracks the Obama campaign’s renewed focus on the economy and special interests in recent days.

Along with ad spending, MoveOn is also investing heavily in Obama-style grassroots organization, through voter registration and turnout, aimed especially at younger voters. MoveOn is fielding 200,000 volunteers (up from 70,000 in 2004), and has a goal of registering half a million voters aged 18 to 29 years. Working with the group Progressive Future, MoveOn is opening 115 field offices in 14 battleground states.

There was a time, not so long ago, when the Obama campaign wanted to see such enthusiasm channeled into its own operations in terms of advertising, fundraising and field operations. The campaign is still engaged in extensive fundraising on its own behalf. But it has grown far more tolerant of outside groups ramping up, at a time when the GOP has expanded its fundraising – and conservative external groups have emerged – in the later stages of this long election.