With less than three weeks to go until the Iowa caucuses, three conservative underdogs fighting for the Republican presidential nomination -- U.S. Rep. Michele Bachmann of Minnesota, Gov. Rick Perry of Texas and former U.S. Sen. Rick Santorum of Pennsylvania -- continued this week to focus on the Hawkeye State as they looked to score a breakthrough in the race.

A poll from Public Policy Polling, a firm with connections to prominent Democrats, released on Tuesday, found that they have their work cut out for them. The three candidates leading the national polls -- former U.S. House Speaker Newt Gingrich, U.S. Rep. Ron Paul of Texas and former Gov. Mitt Romney of Massachusetts -- also lead in Iowa.

Gingrich takes 22 percent, with Paul right behind him at 21 percent. Romney is in third with 16 percent, followed by Bachmann with 11 percent. Perry takes 9 percent, with Santorum taking 8 percent. Former Gov. Jon Huntsman of Utah garners 5 percent, while former Gov. Gary Johnson of New Mexico, who is rumored to be dropping out of the Republican race to run for the Libertarian nomination, takes 1 percent. The poll of 555 likely Iowa Republican caucus voters was taken Dec.11-13 and had a margin of error of +/- 4.2 percent.

Bachmann, Perry and Santorum are all looking to tap into the segment of religious and social conservatives who constitute a large part of the Iowa Republican party. These voters helped propel evangelical leader Pat Robertson into second place -- ahead of then-Vice President George H.W. Bush -- in the 1988 Iowa Republican caucus. They also helped garner strong showings for Alan Keyes and Gary Bauer in the 2000 caucus, and helped push Mike Huckabee to win there in 2008.

While she won the Iowa Republican straw poll in Ames in August and has been playing up her roots in the Hawkeye State, Bachmann has been eclipsed by a series of other conservative candidates -- Perry, businessman Herman Cain who pulled out of the race earlier in the month and, currently, Gingrich.

Looking to get back on track in Iowa, Bachmann unveiled a major endorsement in the Hawkeye State on Wednesday when state Sen. Merlin Bartz, R-Grafton, announced he was backing her bid. First elected to the Iowa Legislature in 1990, Bartz has served a term in the House and is in his fourth term in the Senate. He currently serves as assistant Senate leader.

“Merlin Bartz has been a strong voice on the front lines to defend traditional marriage and family values,” Bachmann said in a statement. “He is a rock-solid conservative and I’m proud to have him standing up for our cause when it matters most -- in these crucial weeks leading up to the first-in-the-nation Iowa caucuses.”  

Earlier in the week, Bachmann’s team announced that they were taking a page from Santorum’s playbook and would make campaign stops in all 99 counties in Iowa before the caucus on Jan. 3. Bachmann will start this campaign swing in Northwest Iowa on Friday and continue throughout the weekend.

“Michele Bachmann is determined to win the Iowa caucuses the same way she won the Republican Party of Iowa straw poll in August -- she’s going to work harder than any other candidate in the race,” Keith Nahigian, Bachmann’s campaign manager, said when the tour was announced on Monday. “Visiting counties over the course of 10 days will reflect her energy, enthusiasm and extraordinary work ethic, as well as her commitment to representing the concerns of Iowa families who want a president that will put them first.”