Heading into the home stretch of the May 18 primary race for the GOP nomination in Oregon’s highly competitive 5th district, the frontrunner, if there is one, remains anybody’s guess. But that hasn’t stopped either contender — Jim Zupancic or state Sen. Jackie Winters — from claiming the momentum.

“Our organization is firing on all cylinders,” said Zupancic.

“I have four words for you: Pump up the volume,” countered Winters campaign manager Darryl Howard. (Last week Winters was forced to briefly suspend her campaign when her 11-year-old granddaughter underwent surgery for a brain tumor, but Winters has since returned to the hustings).

Both Winters and Zupancic present attractive options for Republicans in their desire to knock off four-term Rep. Darlene Hooley (D) in the swing Willamette Valley district.

Winters is the former owner of Jackie’s Ribs restaurants and a long-term member of the state Legislature from Salem. Zupancic, a businessman and Lake Oswego attorney, is a former school board member who ran unsuccessfully for the state House in 2002.

“It’s a tossup,” said Oregon GOP political consultant Jack Kane.

Privately, however, some state GOPers maintain that nominating Winters, the first black Republican woman to be elected to the state Legislature, would be a major coup. And it’s no secret that Winters has suggested that none other than President Bush encouraged her to run.

According to one key Oregon Republican source, the potential of having “an African American of moderate perspective … running against a Democratic incumbent woman,” presented a very advantageous dynamic for the Party of Lincoln.

Winters has capitalized on her legislative perch to rack up just about every important primary endorsement on the books — from the NRA to the Oregon Forest Industries Council — as well as most of the major papers, including The Oregonian, the Statesman Journal and Zupancic’s hometown paper, The Lake Oswego Review.

Oregon Right to Life has co-endorsed both Zupancic and Winters.

Winters also enjoys a substantial financial advantage. Through April 28 she posted $91,162 on hand compared to Zupancic’s $56,590. He has loaned his campaign $150,000.

But the Zupancic camp believes its conservative economic message puts it on the right side of the issues. And earlier this week, Zupancic did pick up the nod from an influential anti-tax group, Citizens for a Sound Economy.

Moreover, Zupancic campaign manager Devon Lyon pointed to a poll conducted for the campaign in early May by Mercury Public Affairs that showed Zupancic with a slight lead, though he conceded the percentage of undecided voters hovered at roughly 50 percent. Lyon declined to release further details.

Winters has not conducted any polling since a February survey by pollster Bob Moore showed her ahead, though campaign manager Howard did admit to having made “a few calls.”

KGW News Channel 8, a local NBC affiliate in Portland, is expected to release new polling Friday that includes the 5th district.

Given the high percentage of undecideds, Zupancic has launched an aggressive media campaign aimed at blunting any name identification advantage enjoyed by the sitting state Senator.

While Winters has relied on direct mail to get her message out, Zupancic has been up throughout the district since mid-April with a TV spot on local broadcast and cable channels emphasizing what he said was his “core message of less spending and lower taxes.”

“Jim Zupancic is doing a good job at appealing to a more conservative Republican primary voter,” said Oregon political analyst Jim Moore. “His TV ads call her a liberal in big capital letters.”

However, he added: “She is someone who is well known in Salem and some of the agriculture areas … . His pedigree is one of a downtown Portland lawyer, which doesn’t really play well on your average mint farm.”

Jim Moore said Tuesday’s election would be the first real test of what affect, if any, the 2001 redistricting has had on the seat, which stretches from Portland to the Oregon coast and includes Salem, the state’s capital. “Now it goes almost into the heart of downtown Portland,” he said, adding that that could mean a boost for Zupancic’s chances.

But Kane maintained that Winters retained the upper hand because of the strength of her support in Marion County, the district’s most populous county and home to Salem.

During the campaign, Zupancic has been relentless on the issue of taxes, hammering Winters for supporting a proposed $1.2 billion tax increase, which Oregon voters rejected — and most state Republicans even more emphatically opposed — in February.

“We think [Measure 30] is illustrative of her position to have bigger government and higher taxes,” Zupancic said. “It’s symbolic about one’s philosophy on government.”

“In some ways being a one-note candidate has hurt him because he’s put all of his eggs in the Measure 30 basket,” asserted Howard.

And that hasn’t stopped the Winters campaign from counter-charging that Zupancic’s criticisms smack of hypocrisy given that he wrote in a 2002 Coalition for School Funding questionnaire that he would support legislation needed to fund public education, even if it meant increased taxes.

“You can’t be all things to all people,” said Howard.

Howard also accused the Zupancic campaign of being “pretty nasty,” of filing “frivolous [Federal Election Commission] complaints against us” and insinuating that Winters — who is 67 — is too old to run.

In turn, the 52-year-old Zupancic criticized Winters for having “ducked out of 12 or 13 joint appearances.”

Still, despite the accusatory tenor of the campaign, National Republican Congressional Committee spokesman Carl Forti said national GOPers were pleased with what they saw so far, praising the pair as “two qualified candidates … who have shown an ability to raise money.”

“The good thing about a spirited primary is that everybody’s dirty laundry gets aired,” he added. “If anything, it makes whoever emerges that much stronger.”

Kevin Mannix, chairman of the Oregon Republican Party, said the party would be pleased with whoever emerged triumphant.

“While we have had fine candidates in the past, either Zupancic or Winters offers us an opportunity to present a solid conservative/moderate image to voters as opposed to Hooley’s liberal image,” he said.

What’s more, the state party is planning a “more aggressive get-out-the-vote effort … than before” and expected the “positive coattails” of the presidential election to boost its eventual House nominee, Mannix said.

However, despite the roughly 10,000 voter registration advantage the GOP enjoys in the district, Hooley has won her past three general elections by healthy margins, in part because “she’s voted pretty much with the views of the people in the district,” Kane said.

But this year — though Hooley is still widely viewed as the frontrunner in any potential general election matchup — the four-term Congresswoman’s campaign manager, Jeston Black, conceded, “It’s more competitive because Republicans in D.C. have taken a vested interest in the race that they haven’t in the past.”

Hooley is facing her own primary challenge on Tuesday. But her Democratic opponent, Manzanita businessman Andrew Kaza, who has about $3,000 in his campaign war chest, is hardly a match for an incumbent who already has more than $1 million on hand for her re-election effort.

“We’re not overly concerned, but we are not taking it for granted,” Black said.