COLORADO SPRINGS, Colo. — Former Rep. Bob Schaffer’s (R) hopes of upsetting Democratic Rep. Mark Udall in Colorado’s open-seat Senate race lies in the hands of independent voters.

Just ask Schaffer, who is running to succeed retiring Sen. Wayne Allard (R).

During an El Paso County Republican Party unity rally Saturday at the Flying W Ranch in the hills overlooking staunchly conservative Colorado Springs, he pointedly urged a crowd of about 225 Republican activists to focus their efforts on persuading voters registered as unaffiliated.

“This is our crucial moment,” Schaffer said before an enthusiastic crowd. “This is when we decide the outcome of elections. This is when we decide that the values we care for are important enough that we’ll give up Saturdays. … We’ll give up time to make that argument — no matter how much of a nuisance it may seem — to persuade that unaffiliated voter.”

Colorado independents lean slightly conservative yet have swung big statewide races toward the Democrats in recent years, helping them pick up a Senate seat, the governorship and two House seats.

Schaffer wasn’t the only one at Saturday’s rally to emphasize the importance of securing the unaffiliated vote. Speaker after speaker — whether discussing a state legislative seat or the very close presidential contest in Colorado between Sens. John McCain (R-Ariz.) and Barack Obama (D-Ill.) — asked their fellow activists to prioritize independent voters in their get-out-the-vote activities this fall.

El Paso County GOP Executive Director Nathan Fisk said independent voters in Colorado tend to agree with Republicans on major issues like national defense, and he emphasized the need for his party to go out and reclaim them for Schaffer to be successful.

“It’s critical that we not only make sure the Republican base gets out to vote, but that we’re talking to unaffiliated voters who share our values,” Fisk said. “We think that’s really where the key lies.”

The results of recent elections illustrates Fisk’s analysis, with independents and even a significant bloc of historically Republican voters helping to lift Democrats to victory in Colorado in the 2004 3rd district race, the 2004 open-seat Senate contest, the 2006 7th district race and the 2006 gubernatorial contest.

Republicans hold a voter enrollment edge over Democrats in Colorado — a 78,277-voter lead as of July 31. However, it has narrowed since November 2006, when it was 165,423. Meanwhile, the number of unaffiliated voters has increased by 9,259, according to the secretary of state’s office.

Udall, who is vacating the solidly Democratic Boulder-area 2nd district, has a head start, leading in every poll taken on this race since it crystallized last summer, including in a Denver Post/Mason-Dixon Polling & Research poll released on Sunday that showed Udall ahead of Schaffer 47 percent to 37 percent.

But the issue of rising gasoline prices has put Udall on the defensive of late — at least enough that the otherwise staunch environmentalist in a recent television spot called for the responsible drilling of domestic oil as a part of a comprehensive blueprint to lower energy costs. Steve Mize, 47, illustrates the challenge Udall might face down the stretch of the fall campaign. Mize owns Jerry’s Market, a mid-sized grocery store that caters heavily to Hispanic immigrants in a working-class Greeley neighborhood.

In 2004, he was a typical Colorado crossover voter, choosing President Bush over Sen. John Kerry (D-Mass.) and Sen. Ken Salazar (D) over beer magnate Pete Coors (R) in the open-seat Senate race.

Concerned about the direction Obama might take the country, Mize plans on voting for McCain in November. But he’s not yet sold on Udall.

“What I’m looking for now is something different,” Mize said. “Everyone in office now isn’t getting it done.”

Mize told Udall during a campaign stop at his market last week that rising gas prices are having a negative effect on his business’ bottom line, his employees’ earning power and his customers’ purchasing power. Mize said the economic squeeze created by high gas prices has made it that much more difficult for him to afford his employees’ health insurance.

The poll notwithstanding, Schaffer believes the politics of gas prices — as characterized by Mize’s concerns — have reframed this race and given him a decided advantage.

“It’s not just the energy issue. It’s the constant, persistent efforts of Mark Udall to drive the price of energy up,” Schaffer said in an interview.

As Schaffer moves to paint Udall as out of touch on energy and too liberal for mainstream Colorado voters, the Democratic Senatorial Campaign Committee has been running TV ads accusing Schaffer of being too cozy with oil companies. And Udall is working to define the Republican as partisan, unreasonable and unethical.

Udall regularly touts his record of working with Republican state legislators and GOP members of the Colorado Congressional delegation — particularly his work with Rep. Marilyn Musgrave to pass a line-item veto. Musgrave is viewed as one of the more conservative House Members.

“You also have to throw into the mix the actions of Congressman Schaffer over the past few years that questions his judgment,” Udall said in an interview while lunching on tacos following his meeting with Mize.

Among other things, Udall referred to Schaffer’s association with an individual convicted of misappropriating an earmark and, subtly, to his connection to disgraced GOP lobbyist Jack Abramoff.

“Those actions draw into question: Is Congressman Schaffer interested in serving the people of the state or his own personal prospects?” Udall said.

With absentee ballots scheduled to be mailed out in the first few days of October and a significant mail-in constituency projected, time to influence voters in this race is drawing short. Early voting begins around Oct. 20.

For Schaffer to pull off the upset, he will need to maximize voter turnout in staunch GOP counties such as El Paso, which encompasses the Air Force Academy and several national conservative organizations, as well as exurban Denver counties such as Douglas.

Schaffer must also perform exceedingly well in the rural counties. Both Salazar and first-term Gov. Bill Ritter (D) were able to win their races in part because of their strength in Colorado’s vast rural territory. Ultimately, however, this race could be won and lost in the Denver suburbs of Jefferson County — commonly referred to in Colorado as “Jeff-Co” — and Arapahoe County.

Schaffer’s chief strategist is Dick Wadhams, who steered Allard to victory in 1996 and 2002. He said the voters of Jefferson and Arapahoe counties in past elections helped elect Allard and former Gov. Bill Owens (R), while helping push Salazar and Ritter over the top in 2004 and 2006, respectively.

Jefferson and Arapahoe counties are “where the preponderance of these independent-minded voters are, who go back and forth in every election” Wadhams said. “They voted for Allard and Owens; they voted for Ritter and Salazar. And now they’re up for grabs again.”