After weathering millions of dollars spent against her in a June 2004 special election and the subsequent November general election, South Dakota Rep. Stephanie Herseth (D) appears headed for a much easier re-election in 2006.

While Republicans continue to present a brave public face about their chances, high-level party strategists privately acknowledge that their best opportunity to knock off Herseth has passed.

“She faced down a very well-funded GOP opponent both in a special election and a general election with the president at the top of the ballot,” said one top Republican strategist. “Until she decides to run for governor or Senate, she will be tough to beat.”

Herseth’s office, however, sounded a note of caution about her re-election prospects.

“South Dakota is a conservative state and a tough district,” said Herseth spokesman Russ Levsen. “We fully expect a competitive race.”

The leading GOP name mentioned to take on Herseth is Matt Zabel, chief of staff to Sen. John Thune (R). Prior to his stint with Thune, Zabel served as a deputy associate attorney general at the Justice Department.

Zabel did not return a call seeking comment on his potential interest in the contest.

Former state Sen. Larry Diedrich (R), who lost both the special and general elections to Herseth, is also seen as a potential candidate.

On its face, the South Dakota at-large district seems an alluring target for Republicans, as the state gave President Bush 60 percent in 2004.

That makes Herseth’s district the sixth-most Republican seat currently held by a Democrat, a list that includes Texas’ 17th district (Bush 69 percent, held by Rep. Chet Edwards), Mississippi’s 4th district (68 percent, held by Rep. Gene Taylor), Utah’s 2nd (66 percent, held by Rep. Jim Matheson), Missouri’s 4th (64 percent, held by Rep. Ike Skelton) and North Dakota’s at-large seat (63 percent, held by Rep. Earl Pomeroy).

As a result of the redness of Herseth’s state, she is one of 10 members of the Frontline Democrats, a group of the Caucus’ most vulnerable incumbents who will receive significant financial assistance from leadership and Members in safer districts. She ended 2004 with just $15,000 in her campaign account but has shown a capacity to raise millions if necessary.

Democrats — and even many Republicans — believe that there are major differences between 2004 and 2006 that make challenging Herseth this time a difficult task.

The first major hurdle for would-be Republicans is that turnout in a midterm election is significantly lower than in a presidential election year, with the difference made up almost entirely of conservative-leaning voters.

As evidence, compare the turnout in the 2002 and 2004 South Dakota Senate races.

In 2002 — a midterm election — Sen. Tim Johnson (D) defeated then-Rep. Thune 49.62 percent to 49.47 percent. Johnson took 167,481 votes to Thune’s 166,957, while a third-party candidate drew 3,070 — a total of 337,508 votes cast.

Two years later, Thune knocked off then-Senate Minority Leader Tom Daschle (D) 51 percent to 49 percent, taking 197,813 votes to Daschle’s 193,279. The 391,092 total votes represented a 16 percent increase from the 2002 turnout.

The second challenge in defeating Herseth is that she has been careful to craft a moderate image during her first months in Congress.

She joined the Blue Dog Coalition, a group of moderate and conservative House Democrats and has introduced a handful of bills — including extending medical care for military reservists and protecting the state’s beef industry — that serve to reinforce her pledge to put South Dakota’s interests above loyalty to the party.

During the special election, Republicans painted Herseth as a clone of the national Democratic Party, highlighting her support for abortion rights and casting her as a proponent of higher taxes.

That message got Diedrich within 3,000 votes but could not get him over the top, and a similar-themed campaign in November saw Herseth triumph 53 percent to 46 percent.

“From the time she was sworn in in June to the election in November she was able to demonstrate the approach she was going to take in Congress,” said Steve Murphy, who handled the media strategy during Herseth’s two 2004 races. “In a full two-year term she has even more of an opportunity [to show] that she means it.”

National Republicans will be carefully watching how Herseth votes in the next 18 months in hopes of finding an issue that could galvanize a challenger.

“A lot depends on her voting record going forward,” said a party strategist. “But so far, Herseth has been very careful.”

With Herseth’s re-election to the House currently on solid ground, the talk in South Dakota political circles has turned to when she will run for higher office.

A gubernatorial race seems most likely as Gov. Mike Rounds (R), who is favored to win re-election in 2006, will be term-limited out of office in 2010 — creating an open-seat scenario.

Gubernatorial runs are common in Herseth’s family.

Her father, Lars, ran for governor in 1986, winning the Democratic primary but losing narrowly in the general election. Ralph Herseth, the Congresswoman’s grandfather, sought the governorship four times. He won once, serving as the state’s chief executive from 1958 to 1960.

Johnson is up in 2008 but is expected to run again. Herseth could challenge Thune in 2010 but would enter the race as an underdog.