Last week, Republican U.S. Senate candidate and former Lt. Governor Jane Norton received a lot of attention for her 46-37 lead in a new Rasmussen poll over incumbent appointee Michael Bennet. Rossputin did a good job of summarizing the results.

One Norton primary challenger, Weld County District Attorney Ken Buck, showed a smaller lead of 42-38. Afterward, Buck told RMA blogger Don Johnson that the poll results show he can win in the general election.

Even so, what makes the strongest case on Buck’s behalf is the trend line. What do I mean? Look at the only clear apples-to-apples comparison: a pair of Rasmussen surveys conducted a few months ago.

On September 16, the day after she officially announced her candidacy, Jane Norton was leading Michael Bennet 45-36. Her 9-point advantage (now at 46-37) is steady and unchanged.

On the other hand, a September 10 Rasmussen poll showed Ken Buck trailing Michael Bennet 43-37. That means in three months’ time he has made a 10-point rally. In absolute terms, Buck may not have the same edge over Bennet as Norton does, but the past three months have greatly closed the gap.

I asked Walt Klein, general consultant for the Ken Buck campaign, what he believes might explain the trend. “It suggests to me that slogging through the grassroots is beginning to pay off [for Buck], and that Norton still has a long way to go,” he said.

Klein also noted that a three-point gain over three months in the Rasmussen survey earned a Denver Post headline for GOP gubernatorial hopeful Scott McInnis, while Buck’s surging poll numbers scarcely merited a mention.

As for Colorado’s other Republican senatorial candidates, Tom Wiens has a 1-point lead over Bennet in the new poll. But it was the first time the two names were surveyed together. So it’s too early to develop trend lines for the former state legislator from Douglas County. And I don’t expect Rasmussen to poll Cleve Tidwell any time soon.