In a September 5 online chat, Washington Post national political reporter Jonathan Weisman claimed of the finding that Sen. John McCain voted in line with President Bush 90 percent of the time, “The 90 percent figure is true, but I cover Congress. The vast majority of those votes are procedural, and virtually every member of Congress votes with his or her leadership on procedural motions.” In fact, Congressional Quarterly's finding that McCain had voted with Bush 90 percent of the time was based on an analysis of “votes where the editors of Congressional Quarterly determined that President Bush had taken a clear position prior to the vote.” CQ gave no indication that the “vast majority” of the votes it analyzed to determine presidential support were procedural votes.

CQ separately analyzed how often members of Congress voted with the majority of their party in “all roll-call votes where an absolute majority of one party voted against an absolute majority of the other party.” According to CQ, McCain voted with his party 81 percent of the time.

CQ, a nonpartisan publication, describes its process for determining presidential support as follows:

Presidential Support: This analysis uses all votes where the editors of Congressional Quarterly determined that President Bush had taken a clear position prior to the vote. There were 443 such votes in the House during the period (9 percent of the total) and 564 such votes in the Senate (22 percent).

On average, House Republicans supported Bush on 80 percent of such votes and Democrats supported the president on just 20 percent. In the Senate, where votes on confirmations tend to elevate presidential support scores, Republicans voted with Bush 88 percent of the time, and Democrats gave him their support on 51 percent of the relevant votes.

CQ describes its party unity score as follows:

Party Unity: This analysis looks at all roll-call votes where an absolute majority of one party voted against an absolute majority of the other party. There were 2,675 such votes in the House during the period (52 percent of the total) and 1,505 such votes in the Senate (58 percent).

From Weisman's September 5 washingtonpost.com chat:

Anonymous: Sen. Obama says a McCain Administration would not represent a change from Bush administration policies since Sen. McCain has voted in favor of Bush 90 percent of the time. Is this true?

Jonathan Weisman: The 90 percent figure is true, but I cover Congress. The vast majority of those votes are procedural, and virtually every member of Congress votes with his or her leadership on procedural motions.

That said, on the two fundamental issues of the campaign -- the Iraq war and economic policy -- McCain and Bush are indeed pretty much on the same page.