"Michigan- 52% of voters think Romney should release 12 years of his tax returns" [View all]

[ProSense]

...Michigan- 52% of voters think Romney should release 12 years of his tax returns to 42% who think he should not. Among independents the breakdown is 59/36.

http://www.publicpolicypolling.com/main/2012/09/obama-up-7-in-michigan.html

As for the overall, Obama is up 7 points, but note that this is PPP's first likely voter poll in MI. These samples tend to lean Republican. The shift from registered voters may have contributed to the narrowing margin.

PPP's first likely voters poll in Michigan this year finds Barack Obama with a solid lead in the state, 51-44. That's down a good bit from our last registered voters poll in July which found Obama ahead 53-39. That's a reflection of the fact that the state could be looking at a very different electorate in 2012 than it had in 2008. We find that 34% of likely voters on this poll are Republicans compared to 33% who are Democrats. Exit polls last time showed 41% of voters as Democrats and just 29% as Republicans.

Then it gets worse for Mitt:

...Michigan voters just don't embrace Romney. Only 45% have a favorable opinion of him to 49% with an unfavorable one. They don't accept Romney as one of their own either- only 34% consider him to be a Michigander to 57% who do not... definitely not helping Romney in Michigan is the position he took on the auto bailout. 53% of voters think Obama has been better for the automotive industry in the state compared to only 31% for Romney. And this is something voters care about- 80% of voters say the candidates' record on the automotive industry is important to them, and 48% deem it to be 'very important.'

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The Republican convention doesn't seem to have done Romney a lot of good in Michigan. Only 30% of voters say it made them more likely to support the GOP this year while 35% say it actually made them less likely to do so, and an equal 35% say it didn't make a difference to them either way...