With votes already being cast in Colorado’s open 6th district Republican primary, the Aug. 12 contest appears to be Mike Coffman’s to lose, as he’s being forced to fend off a formidable assault from Wil Armstrong.

Armstrong, a political novice who is also the son of former Sen. Bill Armstrong (R-Colo.), received a strong boost on Tuesday from former Republican presidential candidate Mitt Romney, who endorsed the businessman over Coffman, Colorado’s secretary of state. Romney won Colorado’s presidential nominating caucus before dropping out of the race, and access to his 6th district supporters could prove invaluable to Armstrong.

But by the Armstrong campaign’s own admission, Coffman still maintained a single-digit lead in internal polling data that is less than a week old. Coffman, who has thrice been elected statewide, has superior name identification, and has specifically geared his advertising and grass-roots campaigns to account for absentee voting, which began on July 12.

“There was still a lot of undecided folks out there,” Armstrong campaign spokesman Jack Stansbery said. “Once we get Wil’s message and name ID up, we have a really good chance of winning. That’s playing itself out now. The 20 percent undecided — that’s great news for us.”

Sean Tonner, a Republican political consultant based in Colorado acting as an unofficial adviser to Coffman, predicted that the secretary of state would win by more than 10 points.

Tonner pointed to an early June poll conducted for Coffman by the Tarrance Group that showed him leading Armstrong by 29 points. In that same poll, Coffman’s numbers were even greater among older voters, who are among the most reliable participants in elections.

Armstrong is currently on broadcast and cable television with his fourth ad; the latest is a hard-hitting contrast piece painting himself as a “career businessman with a record of success” and Coffman as a “career politician with a record of controversy.” Coffman is currently on broadcast and cable television with his fourth ad, a biographical spot.

However, Armstrong went dark in June and didn’t go on the air again until July 7, a crucial period for advertising considering absentee ballots began hitting mailboxes on July 12. Tonner said up to 75 percent of voters in this race might vote absentee, with 60 percent of those who requested mail ballots having already sent theirs in. That figure is expected to hit 70 percent by next week.

“That’s why I tend to believe [Coffman’s victory] will be north of 10 points,” Tonner said.

Rep. Tom Tancredo’s (R) decision to retire from the solidly conservative, suburban Denver 6th district spawned a GOP primary field that is four deep, with the winner of the Aug. 12 contest expected to cruise to victory in November. Aviation consultant Hank Eng is running for the Democrats.

The other two candidates in the GOP primary, state Sens. Ted Harvey and Steve Ward, are not expected to make too much noise when the final votes are tallied. But Harvey’s base is strong in Douglas County, among the two biggest counties that fall within the 6th district, and both he and Ward could cause problems for Armstrong.

Coffman is a known quantity, and Armstrong’s prospects of overtaking him depend on his ability to solidify that bloc of voters that is not inclined to back the secretary of state. Those voters have three candidates to choose from, and that could be a problem for Armstrong, a fact the Coffman campaign gleefully acknowledges.

“We have a candidate who’s won statewide three times,” campaign spokesman Dustin Zvonek said. “It’s almost as if he’s an incumbent.”

Coffman closed the second quarter with $222,000 in cash on hand; Armstrong finished the period with $163,000.

On one thing, the Armstrong and Coffman campaigns both agree — and that is that this race has been about leadership, not any disagreement on key Republican issues.

The Coffman campaign believes its candidate will benefit from that fact. The secretary of state is a military veteran who served in Iraq, and Republicans are used to voting for him.

But the Armstrong campaign is equally encouraged. At a time when Congress’ approval ratings are at all-time lows and the economy is slowing, Armstrong’s status as a businessman who has never run for political office is appealing, according to his supporters.

And because Coffman’s election to Congress would leave the Colorado secretary of state’s office vacant, leaving the job of appointing a replacement to Democratic Gov. Bill Ritter, Armstrong’s backers believe GOP primary voters might choose someone other than Coffman simply to preserve Republican control of the office at a time when Democrats hold most of the power in Colorado.

“It will be a 1- or 2-point race,” said Patrick Davis, a GOP consultant based in Colorado and an Armstrong supporter. “The rub against Coffman is, if he wins he has to step down from one of only two statewide offices Republicans hold in the state. … In a Republican primary, in a four-person race, that will make a difference.”