Conventional wisdom, if you’ll pardon the pun, held that John McCain’s bounce this week came from a party that suddenly discovered enthusiasm from its base.  Gallup’s internals from its daily tracking poll tell a completely different story.  His bounce comes from a significant shift among independents and even some Democrats:

John McCain’s 6 percentage-point bounce in voter support spanning the Republican National Convention is largely explained by political independents shifting to him in fairly big numbers, from 40% pre-convention to 52% post-convention in Gallup Poll Daily tracking.

By contrast, Democrats’ support for McCain rose 5 percentage points over the GOP convention period, from 9% to 14%, while Republicans’ already-high support stayed about the same.

The surge in political independents who favor McCain for president marks the first time since Gallup began tracking voters’ general-election preferences in March that a majority of independents have sided with either of the two major-party candidates. Prior to now, McCain had received no better than 48% of the independent vote and Obama no better than 46%, making the race for the political middle highly competitive.

In fact, Republicans didn’t shift much at all, trans-convention.  Most of the bounce came from “pure” independents, whose support almost doubled from 20% to 39% in a week.  McCain has opened a 15-point gap among independents overall, by far the widest gap in the race to this point.  In contrast, the Democratic convention only provoked a small bump in this demographic for Obama, one that quickly evaporated.

McCain also scored among Democrats.  Overall, he increased his draw by more than half, from 9% to 14%.  Most of that came from conservative, “Blue Dog” Democrats, where McCain gained 10 points from 15% to 25%.  Even his support among self-described “moderate” Democrats increased by five points, from 11% to 16%.  Gallup even showed a two-point gain among liberal Democrats, but going from 2% to 4% probably is more polling noise than a real move.

What does this mean for the election?  It’s both danger and opportunity.  These gains are likely shallow in depth, at risk if Obama can start succeeding in running to the center.  On the other hand, it shows how unsuccessful he has been so far in doing so.  The more people see of Obama, the more voters see him as a doctrinaire, hard-Left liberal and/or unqualified to run the nation as his first executive position ever.  Either of those will become poisonous to Obama’s chances to gain the center in November.