COLORADO SPRINGS - Flying high above the Rocky Mountains on Wednesday, Rep. Paul Ryan and his brother Tobin jogged their memories to complete a list of the 14,000-foot summits below them that the vice presidential nominee had climbed.

"We did that one, we did that one," they said, consulting a list of Colorado's famed "Fourteeners."

It was not an idle pursuit. After Ryan walked back a claim to have run an exceptionally fast marathon, scrutiny has fallen on his other sporting pursuits, including whether he might have exaggerated his mountain-climbing prowess. In this case, the brothers figured that over 20 years of visits to Colorado, he had climbed above 14,000 feet "probably 38, 39 times" -- potential ammunition against the doubters.

Four weeks ago, no one would have questioned such a detail of Ryan's résumé. But since joining the Republican ticket, every scintilla of his life, every statement he has uttered, has been open to inspection. His marathon claim was debunked by Runner's World, hardly known for political investigations.

There is perhaps no faster escalator to political superstardom in the United States than to be plucked as a vice presidential candidate. Mitt Romney has spent six years seeking the presidency, but for Ryan, the overnight ascension and all its trappings -- speaking to millions in prime time at the Republican National Convention, a motorcade that stops traffic, imprisonment in a Secret Service bubble -- have left little time to adjust.

"He can't believe all this is going on around him," said a senior adviser to Ryan.

Longtime aides and family members say he is the same person they have always known and has risen to the challenge, even though the cumulative effect on the ticket of some recent stumbles has yet to be measured.

"People were kind of afraid for us and for Paul, thinking this is going to be overwhelming," said Tobin Ryan, his older brother by five years. "It's been the opposite. I see my brother -- it amazes me day after day he rises to another level and wants to do more."

Tobin Ryan remained on the campaign trail when the nominee's wife and their children peeled off after the convention.

After delivering a speech, Ryan immediately seeks his brother's eye for feedback. "We can read each other so well," Tobin said. "All I have to do is glance back and he knows that he did it well."

Other times the feedback is not so positive. "I'll take notes," Tobin said. "I'll say, here are three things." Tobin dinged his brother the other day for saying "most free-est."

Other slip-ups have been less innocent. In North Carolina this week, Ryan accused President Obama of having failed to revive the economy but conflated a statistic for business bankruptcies with much more numerous personal bankruptcies.

The first time he accused the president of having failed to rescue a Wisconsin auto plant, three weeks ago, he implied that high gasoline prices caused by Obama led to the plant's shutdown, even though President George W. Bush controlled federal energy policy at the time.

In each case, after making the faulty assertion, Ryan quickly adjusted his talking points. "He very much wanted to use the same statistic and get it right the next day," Michael Steel, Ryan's traveling spokesman, said of the bankruptcy figure.