For an example of how dramatically redistricting can shift a state’s political makeup, look no further than Colorado’s 6th district — a seat once held by conservative Republican Rep. Tom Tancredo that is now considered a tossup.

Rep. Mike Coffman beat his Democratic opponent by a two-to-one margin in 2010 but finds himself in electoral trouble two years later as he seeks a third term.

The state courts had to resolve redistricting when Colorado’s split-power government was unable to compromise on a new map. This was the fourth time in four decades that Colorado had to resort to this process.

Coffman essentially got the short end of the stick in redistricting within the Republican House delegation. GOP Reps. Scott Tipton and Cory Gardner were also discussed as targets for more Democratic-leaning districts.

Tipton’s district remained a tossup, and Gardner’s was shored up with Republican votes at Coffman’s expense.

Republicans have a 4-to-3 advantage in the Colorado delegation, but Democrats have made clear the path for the Democratic Congressional Campaign Committee’s “Drive for 25” effort to retake control of the House goes right through the West. The DCCC’s anti-Coffman offensive has so far included only robocalls into the district, and he’s also expected to see a lot of activity as President Barack Obama’s re-election campaign focuses its efforts in the region.

Coffman sounded confident as he outlined a demographic he thinks he can win: “Reagan Democrats-turned-Hillary Clinton Democrats.”

“The nature of the Democrats in this Congressional district are somewhat different than Democrats in other parts of the state,” Coffman told Roll Call. “These are more working-class, blue-collar Democrats as opposed to their more liberal counterparts in Boulder and parts of Denver.”

The new 6th district will consolidate the state’s third-largest city, Aurora, into a single district on the western edge of the Denver metropolitan area. The city is ethnically diverse with a large medical sector.

Even though one national Republican strategist admitted that Coffman “will have to work harder” this cycle, the legislator said he feels “pretty good” about the state of the race because he had more than $600,000 in cash on hand after the third quarter and has solid name identification.

It will be an uphill climb as Coffman introduces himself to the 40 percent of his new district’s residents whom he had not represented under the current 6th.

Fifty-three percent of Coffman’s district voted Sen. John McCain in 2008. But under the new lines, Obama would have captured 53 percent of the vote. The voter registration of the new seat is about one-third Democratic, one-third Republican and one-third unaffiliated.

The most organized Democratic challenger to emerge against Coffman is state Rep. Joe Miklosi. He has hired campaign staff and raised $130,000 in the third quarter.

He got a major break last week when former state Speaker Andrew Romanoff endorsed him instead of launching his own campaign. The Democratic field is far from settled. There is an “active rumor mill” in the state, according to Colorado Democratic State Party spokesman Matt Inzeo. “I don’t think we’d be surprised if one, possibly two more, candidates” get into the race, he said.

Inzeo describes the party as “excited” about the Miklosi campaign.

Physician Perry Haney, a former chiropractor, officially threw his hat in the ring for the 6th district’s Democratic nomination on Wednesday. It was previously speculated he might vie with Pace for the Democratic nod in the 3rd district. He is running on the slogan: “There’s nothing wrong with Congress that a spine doctor with a backbone can’t cure.”

Roll Call Politics rates the newly drawn 6th as a Tossup. Republicans believe it is a Leans Republican district.

The narrative Democrats are pushing is that Coffman is too conservative and no longer fits his more moderate district. In a November interview with Roll Call, Miklosi went so far as to describe the incumbent as “radical,” and Democrats call him “extreme,” citing his membership in the Tea Party Caucus and comments comparing Social Security to a Ponzi scheme when praising Texas Gov. Rick Perry (R) in September. Perry’s stance on Social Security has contributed to his slide in polls for the GOP presidential nod.

“My record is absolutely not extreme nor radical, but my guess is what is not true, they’ll make up,” Coffman told Roll Call.

Colorado will be one of the most heavily targeted states in the presidential race, given its swingy nature — it backed George W. Bush in 2000 and 2004, and Obama in 2008 after he accepted the party nod in Denver. Both party’s nominees will benefit from presidential campaign infrastructures. What they will not have are statewide campaigns to piggyback off of volunteer networks. Neither Senator is up for re-election this year, and statewide elections are held in off-years. That means Congressional candidates will appear directly below the presidential candidate names on the ballot. And although the presidential campaigns are expected to make heavy ad buys in the state, the House campaigns will not have to compete with statewide campaigns for ad time.

The Obama campaign is betting big on Colorado in 2012. The state is part of what Obama campaign manager Jim Messina described to reporters last week as “the West path.” He said the Obama campaign intends to campaign heavily in western states such as Colorado, Nevada and New Mexico. The West was “how the Democrats kept control of the United States Senate in 2010,” Messina said.

Correction: Dec. 27, 2011

An earlier version of this article incorrectly identified Haney’s current profession.