Democratic Sen. Amy Klobuchar is the nation's sixth most popular U.S. senator, according to Public Policy Polling, and would easily beat either former Republican Gov. Tim Pawlenty or Rep. Michele Bachmann in a re-election campaign.

The new poll, released Tuesday, also found that few Minnesotans had heard of Klobuchar's announced Republican challengers and she led each of them by 23 percentage points or more. In hypothetical matchups, Klobuchar would get 54 percent to Pawlenty's 39, and the sitting senator would get 58 percent to Bachmann's 35 percent.

Neither Pawlenty nor Bachmann has shown any interest in running against Klobuchar, however.

"Amy Klobuchar continues to be one of the most popular senators in the country and should have little trouble winning re-election," said Dean Debnam, president of Public Policy Polling.

The poll, conducted among 1,236 Minnesota voters Jan. 21-22, found that 61 percent of Minnesotans approve of the job Klobuchar is doing, while 28 percent disapprove. Those numbers are similar to approval ratings Klobuchar received last year.

Pawlenty and Bachmann's popularity ratings are less secure. Both former presidential candidates had more Minnesotans saying they had unfavorable opinions of them than positive. Half of Minnesotans said they view Pawlenty negatively and would not support him should he run for statewide office again. According to the poll, 57 percent of Minnesotans view Bachmann unfavorably.

Democratic Sen. Al Franken, who will be up for re-election in 2014, has also improved his favorability rating since his narrow 2008 election win. Forty-nine percent of Minnesotans approve of the job he is doing, while 39 percent disapprove. Generally, any incumbent who receives less than 50 percent approval from voters is considered vulnerable to challenge.

But according to the poll, neither Bachmann nor Pawlenty would beat him in hypothetical elections. although Pawlenty would come closer. Public Policy Polling found that Franken would get 49 percent to Pawlenty's 43 percent; the sitting senator would receive 54 percent if Bachmann ran against him. She would garner 39 percent.

The poll has a margin of error of plus or minus 2.8 percentage points.

The polling firm, which works with Democrats but has produced numbers that are trusted on both sides of the aisle, will publish more Minnesota-specific numbers in the coming days. It has also polled about the current presidential race, the marriage amendment in Minnesota and the Wisconsin gubernatorial recall election.

Rachel E. Stassen-Berger Twitter: @rachelsb