President Barack Obama's re-election campaign argued Thursday that Mitt Romney's choice of Paul Ryan as his running mate amounted to a "Hail Mary pass" from a campaign trying to reach its conservative base. But a new CNN poll confirmed that the race in Ryan's home state of Wisconsin had tightened into a toss-up from a Democratic edge.

On a conference call with reporters, Obama campaign officials highlighted national polls suggesting that Romney got less of a "bump" from his pick than past candidates and compared Ryan to Sarah Palin and Dan Quayle.

"Elections are about choices and about where you're going to take the country going forward," pollster Joel Benenson said on the call. Team Obama has worked to convince voters that November is a choice between two visions, rather than a referendum on the president's record.

"They've kind of made a Hail Mary pass with this pick to try to say that they're going to make this about a choice too," Benenson said. "They're kind of playing on our turf right now. We think this choice is very good for us. They may be playing for their base, but this is an election that goes beyond just playing for your base."

In a separate memo, Benenson underlined that Romney had gained just 1 point in the Gallup daily tracking poll, while losing 1 point in the Rasmussen equivalent.

"Initial metrics place Romney's choice on a par with the selections of Sarah Palin and Dan Quayle," Benenson wrote.

A Gallup analysis showed that Republican Sen. John McCain got just a 2-point bounce from choosing Palin in 2008. The polling organization said it could not accurately measure the impact of vice presidential picks before 1996, meaning it could not judge how selecting Quayle shaped then-Vice President George H.W. Bush's 1988 run. Republican Sen. Bob Dole scored the biggest bounce, 9 points, with his choice of former Sen. Jack Kemp in his 1996 bid for the White House.

"Although the announcement of Romney's running mate will be one of the more significant events in the 2012 campaign, it has not done much to change voter preferences, at least initially," Gallup said.

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Voters tend to place less stock in the importance of a vice presidential pick than analysts do—people typically cast ballots for the top name on the ticket. And the Romney campaign disputed Benenson's "bogus memo," saying that other picks came just before the nominating convention, or during that event, virtually ensuring a larger bounce.

Romney pollster Neil Newhouse jabbed at the president's campaign, saying it "has just spent $100 million on TV ads since May, most of them negative against Gov. Romney, and they're in worse shape now than when they started."

The Romney campaign got good news from a new CNN/ORC poll that reinforced the idea that Ryan's home state of Wisconsin—which Obama carried by 14 points in 2008—was now a toss-up.