Updated 6:40 p.m. ET

This story has been updated to specify the views of registered voters in the USA TODAY/Gallup Poll about Paul Ryan. It will also appear in Tuesday's editions.

Our original post begins here:

Americans don't believe GOP presidential contender Mitt Romney hit a home run with his choice of Paul Ryan as a running mate, a USA TODAY/Gallup Poll finds, with more of the public giving him lower marks than high ones.

Ryan, a Wisconsin congressman, is seen as only a "fair" or "poor" choice by 42% of Americans vs. 39% who think he is an "excellent" or "pretty good" vice presidential choice.

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Romney pollster Neil Newhouse said in a statement that the findings reflect the fact that Ryan, a House member since 1999, isn't widely known.

USA TODAY/Gallup polls of registered voters after the announcements of running mates since Dick Cheney in 2000 all showed more positive reactions. Only Dan Quayle in a 1988 Harris Poll of likely voters was viewed less positively than Ryan, with 52% rating Quayle as a "fair" or "poor" vice presidential choice. The Ryan poll includes all adults, not just registered voters.

Since Romney introduced Ryan as his running mate on Saturday, Democrats have set out to portray the House Budget Committee chairman as an extremist for his plans to revamp Medicare. President Obama called Ryan an "articulate spokesman" for "a vision I fundamentally disagree with."

"All these numbers indicate is the simple fact that congressman Paul Ryan was not a nationally known figure prior to being named as Gov. Romney's vice presidential pick," Newhouse said. "Congressman Ryan's selection reinforces the seriousness of the issues that will be debated in this election and President Obama's failure to get Americans back to work and his inability to strengthen the middle class."

The poll also finds 17% of adults say they are more likely to vote for Romney in November because Ryan is his running mate -- about the same impact Sarah Palin had for John McCain four years ago among registered voters.

Republicans, however, see the appeal in Ryan, who was hailed this weekend as a bold, innovative thinker by party stalwarts. The poll finds 36% of Republicans are now more likely to vote for Romney. In 2008, only three in 10 Republicans said the choice of Palin made them more likely to vote for McCain.

The USA TODAY/Gallup survey also finds 48% of Americans view Ryan as qualified to be president if something should happen to Romney, while 29% do not and 23% were undecided. Only Palin, then the governor of Alaska, and Quayle, a two-term senator from Indiana, were rated lower than Ryan.

The poll of 1,006 adults was taken Sunday. It has a margin of error of +/-4 percentage points.