Russ Feingold is popular enough with grassroots Democrats to have been boomed as a potential candidate for the party’s 2008 nomination.

He has a national reputation for working across lines of party and ideology; in fact, Republican presidential candidate John McCain jokes that supporters of campaign finance reform think that “Feingold” is his last name.

Feingold comes from a battleground state that both the Democrats and Republicans say is critical to their strategies for accumulating the 270 electoral votes needed to secure the presidency.

Because of the bold stands he has taken as a defender of civil liberties, an advocate for the withdrawal of U.S. troops from Iraq and a champion of fair-trade economic policies, he could calm concerns among internet activists and labor stalwarts who have complained about presumptive Democratic nominee Barack Obama’s murkiness on those issues.

And he might even help Obama build confidence and support among older Jewish voters — who have evidenced some skepticism regarding the candidacy of the Illinois senator — in the swing state of Florida.

Yet, as Feingold is the first to assert, “I’m not considered for vice president by anybody; it’s not even a passing thought.”

Why doesn’t Feingold’s name show up on the long short-list, or the even the short long-list, of Obama’s potential running mates?

“I’m too hot to handle apparently,” says Feingold, laughing at the very notion of an Obama-Feingold ticket.

Playing pundit for a moment, Feingold says, “I’m not the ideal mix for a guy like Obama for a huge variety of reasons… He’s a Midwesterner, I’m a Midwesterner. He’s a senator, I’m a senator.”

But then the senator from Wisconsin gets to the point.

“Obama’s looking for someone who would presumably balance the ticket, and I don’t think most people would see me as balancing an Obama ticket,” he explains.

Don’t get Feingold wrong.

He is not one of those who believes it is wise to search for a boring centrist to “balance” Obama’s star power and perceived liberalism. Feingold, who established his Progressive Patriots Fund with the express purpose of “promoting a progressive reform agenda” within the party and nationally, says the Democratic presidential candidate would be best-served by a running-mate with a bold values-driven commitment to challenging the caution and compromises of both major parties.

“I would love it,” the Wisconsinite says of a vice-presidential selection that tips the ticket in a progressive direction. “But that’s not necessarily what (Obama and his aides) are thinking. I think we would all have to agree that hasn’t been their direction since the nomination was cinched.”

Feingold’s not frustrated for himself.

There’s no evidence to suggest that he regrets his decision to seek the presidency this year — or that the fiercely-independent senator would be happy as anyone’s “No. 2.” But he is uncomfortable watching Obama, who won the Democratic nod by taking bolder stands than Hillary Clinton on a number of foreign and domestic policy issues, now edge toward the ill-defined and uninspired center.

“It is always hard to see a candidate, even though I like him very much, move on certain issues in a direction I’m uncomfortable with,” Feingold says. “I hope it’s minimized.”

Beyond hoping that Obama picks a progressive running-mate, Feingold says he is of the view that the Illinois senator should go for someone with stature rather than a base in a swing state.

Though he once suggested that an Obama-Clinton ticket would be politically muscular — and thought he has also speculated about the prospect of former Senate Majority Leader George Mitchell as a strong vice presidential prospect — Feingold’s less interested in naming names at this point than in suggesting a standard that the nominee would be wise to apply.

“I still think that his choosing somebody who has a credibility on foreign policy and military issues — to make sure people are comfortable with the Democrats on that, in light of the instability in the world – is probably the best approach,” explains Feingold. “I don’t think Obama does well by trying to pick somebody who is going to win a state for him. I can understand McCain doing that – with a (former Massachusetts Governor Mitt) Romney, a (Minnesota Governor Tim) Pawlenty or a (former Pennsylvania Governor Tom) Ridge. I think Obama has a different way of running, and that is a national wave of excitement based on his candidacy and a strong ticket. I wouldn’t cherry pick a running mate just to try and carry a state. That’s not what he needs.”