The Colorado Senate race is entering a volatile period, because what was becoming a predictable polling pattern has changed. In a two-month period, from mid-July to the middle of September, Sen. Mark Udall (D) had built a small but consistent lead and appeared perched on the cusp of pulling away. Now, however, according to a just released Public Policy Polling survey, the tables have turned.

The latest PPP data (Sept. 19-21; 652 CO likely voters) finds Rep. Cory Gardner (R-CO-4) now taking a 47-45 percent lead in the habitually tight Senate contest. In fact, after Sen. Udall led in seven consecutive publicly released surveys during the aforementioned two-month period, Rep. Gardner has suddenly secured an advantage on the latest four.

The first poll to project him to a lead, in a spread of eight percentage points, was the mid-September Quinnipiac University survey (Sept. 11-15; 1,211 likely Colorado voters). This study was not taken particularly seriously and became routinely labeled an outlier because its results were so different from any other produced data. With three successive polls also projecting Gardner holding an edge of varying proportions, the Q-Poll findings now appear more reliable.

What makes this Public Policy Polling survey more eye-catching is its sponsors. Conducted jointly for liberal organizations Americans for Tax Fairness and the local ProgressCO, the survey menu contained a series of push questions to firmly establish the respondent on the liberal side of certain tax and environmental issues. It appears that the order of the questions did pose the ballot test before the push questions were asked, but it’s possible that PPP did not publish the final questionnaire order or list all of the responses. Even accepting the published information as complete, which is likely, the fact that Gardner would lead under such circumstances is noteworthy.

In the period during which Udall was ahead, seven consecutive polls yielded him an average advantage of 3.1 percent. In the four consecutive polls in which Gardner leads, from the Sept. 10-21 period, the Republican challenger has an average edge of 4.5 points. This includes the Quinnipiac eight-point spread followed by a Gravis Marketing poll (Sept. 16-17; 657 likely Colorado voters) that projected Gardner to a seven-point advantage. Again, these later results give more credence to the original Q-Poll’s disparaged accuracy.

The Gardner campaign also released their newest television ad, a spot that a spokesman for the Democratic Senatorial Campaign Committee claims is a “disgusting attack” on the Udall family.

The ad features Gardner speaking into the camera, talking about his father and grandfather being agricultural equipment salesmen. He contrasts that with the Udall family’s career involvement in politics, highlighting Mark Udall’s two cousins serving with him in the Senate (senators Tom Udall (D-NM) and Mike Lee (R-UT)), and the fact that his father, former Rep. Morris K. “Mo” Udall (D-AZ-2), had run for president. He also refers to his opponent as a “nice guy.” It’s hard to see how such comments reach a “disgusting” level, but the ad is attached above, so you can have the opportunity of deciding for yourself.

The latest change in polling leaves no doubt that the Udall-Gardner campaign remains a pure toss-up.