Twenty-three percent said the Ryan pick made them less likely to vote for Romney, 22 percent said it made them more likely, and 54 said it had no impact on how they would vote.

Immediately following his selection earlier this month, both sides moved quickly to define Ryan to those who might not know him, but the NBC-WSJ poll indicates Ryan has had little impact on the overall race.

In a Gallup poll released earlier this month, 42 percent said they viewed Ryan’s candidacy as a “fair” or “poor” move by the Romney campaign, compared to 39 percent who said it was an “excellent” or “pretty good” choice.

Still, Ryan’s candidacy could have an impact in his home state. Wisconsin is one of 12 battlegrounds that will be critical in determining the outcome of the 2012 election. According to the latest survey from liberal-leaning Public Policy Polling, Ryan has propelled Romney into the lead over President Obama in the Badger State 48-47, a 7-point swing from the same poll in July, in which Obama led 50-44.

But Democrats have tried to paint the seven-term lawmaker as outside the mainstream, with senior campaign advisers blasting the House Budget Committee chairman’s fiscal plans, and in particular his proposal to turn Medicare into subsidies for private insurance.

The NBC-WSJ poll indicates this might be working — 44 percent say recent news gave them a less favorable opinion of Romney, compared to 32 percent who said more favorable.

In addition, the poll shows Obama with a wide lead over Romney on the issue of Medicare, 50-34.

Somewhat surprisingly, Romney and Ryan have focused on what has typically been a Democratic strong suit, amplifying their attacks on Obama's Medicare reforms, claiming he will gut the popular seniors program, leaving it up to Republicans to save it. 

Democrats have pushed back, arguing that the cuts at the center of the GOP attacks — roughly $700 billion in reductions to projected Medicare growth estimated over the next decade under the Democrats' 2010 reform law — come largely from eliminating waste, fraud and subsidies to insurance companies, not from cutting health benefits to seniors.