Why McCain is doing better in the polls

Blake Dvorak from the WSJ's Political Diary:

Reasons for the McCain Surge? Republicans (not Independents and Democrats)

One surprising finding in last week's Pew Research poll on the presidential election is that Sen. John McCain has stronger support among Republican voters than Sen. Barack Obama does among Democratic voters. Since June, Mr. McCain has increased his support among Republicans by five points, from 82% to 87%. By contrast, Mr. Obama increased his support among Democrats by just one point, 82% to 83%.

These numbers are surprising because they go against conventional wisdom. Mr. McCain was supposed to be the one having trouble with his base, while Mr. Obama was supposed to quickly sew up the schism with Hillary Clinton supporters and unite his party. In fact, according to Pew, Mr. Obama has 72% support from former Clinton backers, exactly where it was a month ago.

So what can we glean from Pew's numbers in terms of optimizing each candidate's respective vice presidential choice? First, although the poll suggests that Mr. Obama should choose Mrs. Clinton, he has likely already made his decision and it's not Hillary, which won't make wooing alienated Clinton fans any easier. For Mr. McCain, who is believed to be still mulling his options, Pew's numbers should bring a sigh of relief as well as a sense of caution. Mr. McCain's relationship with the Republican base has always been contentious, so its support should not be taken for granted. His Veep selection should be aimed at shoring up that support even as he makes a play for the middle. . . .