Larry Pressler, who served three terms as a Republican senator for South Dakota from 1979 to 1997, is looking to make a return trip to Washington. (AP Photo/Dirk Lammers, File)

Larry Pressler doesn't roll deep.

The independent Senate candidate has one paid campaign staffer. His driver is his wife, Harriet. He is his own campaign manager. Compared to his opponents, he's only raised pocket change.

And yet, with less than four weeks until the all-important election in South Dakota, the former senator is a top target in the suddenly-competitive campaign. He's now taking heat from Democrats who say he's too conservative and Republicans who say he's too liberal, the surest sign yet he is picking up steam. In what's been a wildly unpredictable battle for the Senate majority, Pressler may be the least likely star player of all.

Like Greg Orman in Kansas, Pressler has parked himself firmly in the political middle, he won't commit to caucusing with either party in the Senate and has shaken up a race that has long looked like it was a Republican lock. But that's where the similarities end. While Orman is a fresh-faced political newcomer with deep pockets, Pressler is a longtime politician with a bare-bones operation looking for one last hurrah.

In an interview, he embraced the role of underdog and acknowledged that he is likely to get outspent badly during the stretch run of the race.

"I am like a naked little rabbit with all the guys with shotguns starting up the hill," he said.

Pressler's long-shot campaign was complicated Friday afternoon by the revelation that his principal residence is in Washington. As first reported by Politico, Pressler and his wife receive the homestead deduction on their D.C. condo, a tax incentive for people who use their D.C. homes as their "principal residence." Pressler said he and his wife have the D.C. apartment because she works there. He said he rents an apartment in Sioux Falls.

A SurveyUSA poll released this week showed Pressler within striking distance of the frontrunner, Republican Mike Rounds, and ahead of Democratic nominee Rick Weiland. Rounds has been facing heat over his handling as governor of a program that offers green cards to foreigners who invest in U.S. job creation. Meanwhile, Democratic groups have abruptly committed to pumping millions of dollars into the contest.

"The real story is that this frees up money for Weiland to attack me and Rounds already has plenty of money to attack me," Pressler said of the planned outside spending.

Republicans need to gain six seats to win control of the Senate. Losing in South Dakota, where Sen. Tim Johnson (D) is retiring and they have long been favored to win, would be a devastating blow.

"If we do not win in South Dakota we do not take back the U.S. Senate," said Rounds in an interview.

Pressler, 72, is less concerned about political parties. He's pitching himself as the perfect antidote to the gridlock that has seized Washington.

"I offer a practical, problem-solving, moderate approach to governance," he said.

Pressler served in the Senate as a Republican from 1979 until 1997, but supported President Obama in 2008 and 2012. He calls himself a "deficit hawk" who has been disappointed in Obama's record on deficit reduction. But he's not hostile toward the president -- not as hostile as most Republicans, anyway.

The GOP has pounced on Pressler's support for Obama as a sign that he would side with Democrats in the Senate. South Dakota is an increasingly conservative state where Obama lost by a wide margin in 2012.

"The Larry Pressler of 18 years ago is long gone," said Dick Wadhams, a consultant to the state Republican Party. "Don't know what happened to him. Don't know where he went."

Meanwhile, Weiland's allies have started using Pressler's Senate record against him. Every Voice Action, a pro-Weiland super PAC that had been focused on attacking Rounds, just started airing an ad hitting Pressler over his record in the Senate. The commercial claims he voted to cut Social Security and Medicare.

When asked which party he would caucus with in the Senate, Pressler said he would probably side with the party that would assure him roll call votes "on the five or six things" he cares deeply about, like tort reform in health-care.

The uncertainty about Pressler may be part of the reason why national Democrats have decided to lay out resources to fight Rounds: Even if Weiland doesn't win, they may get a Senate ally in Pressler.

The Democratic Senatorial Campaign Committee said this week it would spend $1 million on ads and a field operation. Mayday PAC, a group that wants to curtail the influence of money in politics by electing campaign finance reformers, has committed to dropping $1 million to help Weiland. The liberal group MoveOn is also pitching in for the Democratic nominee.

These are all unexpectedly encouraging signs for Weiland, a former aide to Tom Dashcle who was never his party's first-choice recruit -- or its second -- and who has been written off by many people as too liberal for South Dakota.

"I had a certain level of confidence that this race was going to get competitive, and when it did there would be some interest," said Weiland.

The fresh Democratic interest has come as Rounds is battling attacks over the way he oversaw the "EB-5" program when he was governor. Former state officials who headed up the program to allow foreigners who invest in job creating enterprises to earn green cards came under scrutiny in what opponents have labeled a "citizenship for sale scheme." Rounds insists he did nothing wrong.

But the attention has opened the door for Weiland and Pressler. Rounds, who has run a positive campaign so far, said he plans to draw clear distinctions between himself and his opponents in the final leg of the race, signaling a more aggressive posture.

One of Pressler's biggest assets is that he is well-known in South Dakota from his days in Congress. But as he tries to convince voters he has a forward-looking vision, he can't help but remind them that he is in many ways a candidate from a bygone era.

He's run an ad featuring the late anchorman Walter Cronkite. And in his interview with The Washington Post, Pressler referred to Sen. Mark Pryor (D-Ark.) as his father "David Pryor," who served in the Senate in the 1980s and 90s.

"I'm showing my age there," he said.

Pressler says he would serve only one more term, freeing him from the constraints of raising money and pleasing special interests. And if he loses? He says he's perfectly content returning to a life of teaching, riding his bicycle -- he can do an 18 mile trail in about an hour -- and spending time with his grandchildren.

"I will have tried," he said contently.

Updated at 4:22 p.m.