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A new Minnesota poll, commissioned by a partisan group, finds that Democratic U.S. Sen. Al Franken is "potentially vulnerable" as he mounts his bid for re-election.

It found that Franken has a 3 percentage lead over Republican Julianne Ortman and a 6 percentage point lead over Republican Mike McFadden.

The poll was conducted by Magellan Strategies for American Encore, a group connected to the Koch Brothers that is already running television ads bashing Franken. It included 1,081 likely Minnesota voters in late March.

The numbers in the poll will likely give American Encore and groups like it reason to keep pushing national money into Minnesota.

Minnesotans are nearly equally split on whether Franken is doing a good job as senator with 44 percent saying they approve of his job performance and 44 percent saying they do not, the poll found. Such splits have followed Franken's career -- he won his 2008 election by just 312 votes.

According to the poll, Franken is considerably less popular with Minnesotans than Democratic U.S. Sen. Amy Klobuchar. It found that 57 percent of voters approve of the job Klobuchar is doing Klobuchar won her 2012 re-election with 65 percent of the vote.

But it also found more Minnesotans disapprove of the job President Obama is doing, compared to Franken. The poll found that 53 percent of voters disapprove of Obama's job performance.

Although the poll was commissioned by a partisan organization, many of them are in line with recent non-partisan polling numbers. In February, a Star Tribune poll found that half of Minnesotans disapproved of Obama's job performance. Last month, a Survey USA/KSTP poll found that Franken had single digit leads over some of his Republican opponents.

The poll's sample included 31 percent Democrats, 28 percent Republicans and 40 percent independent or something else. The February Star Tribune poll found that more Minnesotans considered themselves Democrats and fewer independent or something else.