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It's hard to out-conservative Sen. Mike Lee.

He's the most ideologically extreme senator serving today and the most conservative Utahn the state has ever sent to Washington, according to a study by a Brigham Young University professor.

The research, released through, uses a well-respected scoring system called NOMINATE that condenses roll-call votes to a single score.

A perfect conservative score is 1.0, while a perfect liberal score would be minus 1.0. In the last Congress, Lee came in at 0.991. The second-most conservative senator is Rand Paul of Kentucky, with a score of 0.977.

Sen. Elizabeth Warren, D-Mass., is the most liberal senator. But because her score of minus 0.622 was closer to the Democratic pack than Lee's was to the Republicans, assistant political science professor Michael Barber named Lee the Senate's most extreme member.

Lee declined to comment on this analysis.

Elected in 2010, he has been a leader in the tea-party movement. As a result, he's often been to the right of most Republicans on major issues from the budget to health care to immigration.

He has been willing to take more extreme measures, including a standoff that led to a government shutdown, to fight against the Affordable Care Act.

He also has cast himself as a conservative thought leader, delivering a series of speeches on how to turn tea-party ideas into a positive governing agenda focused on reducing poverty and strengthening families.

Barber didn't just look at the scores from the most recent Congress.

He tracked them back to 1896, when Utah attained statehood. Since that time, Utah has sent 49 men and women to represent the state. None had a more conservative score than Lee.

Second place went to Sen. Arthur Brown, who served in the Senate in 1896 and 1897, before the 17th Amendment put the election of senators in the hands of voters instead of state legislatures. Brown had a career NOMINATE score of 0.812.

Within Utah's current congressional delegation, Rep. Jason Chaffetz is the second most conservative, with a score of 0.722, far from Lee's mark. After Chaffetz, comes Rep. Rob Bishop, followed by Rep. Chris Stewart and then Sen. Orrin Hatch. Rep. Mia Love joined Congress in January and is not included in this data.

Lee is up for re-election in 2016, and Barber says "Lee is vulnerable to a moderate challenger in a primary election."

He bases that on an analysis of Lee's conservative scores compared to the views of most Utah primary voters.

While Lee might have a vulnerability, there hasn't been a rush of candidates trying to exploit it yet.

Just this week, former Gov. Jon Huntsman said he wouldn't be a 2016 Senate candidate. Names often floated as potential challengers are Josh Romney, the son of former Republican presidential nominee Mitt Romney, and Thomas Wright, a former chairman of the Utah Republican Party.