The Democratic National Convention is above all about building support for the Obama-Biden ticket. However, I would like to see some progress toward making a case against John McCain this week as well.

There’s been a lot of hand-wringing on the liberal blogs about Obama’s diminishing lead over McCain this summer. Nate Silver/poblano no longer sees Obama as a clear favorite to win the electoral college, while Chris Bowers still sees Obama as a slight favorite, but in a much weaker position than last month. The McCain campaign has spent tens of millions of dollars on negative advertising this summer, and it does seem to have brought Obama’s numbers down.

Who on the Democratic side is to blame? Some people think Obama’s a brilliant candidate suffering from an incompetent press shop. Slinkerwink is sick and tired of “mealy-mouthed” statements in passive voice from the Obama campaign. But it seems clear to me that Obama sets the tone for his own press shop. If he wanted them to go for the jugular, they would be doing it.

For most of this summer, the Obama campaign has been running a lot of positive television ads nationwide, while running targeted, state-specific negative ads against McCain.

For instance, here is an ad tying McCain to Ralph Reed and Jack Abramoff. It seems like inside baseball until you learn that it’s running only in Atlanta. Two years ago, Reed lost the Republican primary for lieutenant governor in Georgia because of his ties to Abramoff:

This ad started running in Ohio in mid-August, linking McCain to a merger that may cost thousands of jobs:

Obama has also run a tv ad in Nevada about McCain’s support for the Yucca Mountain nuclear waste site.

There’s nothing wrong with these ads or making a state-specific case against McCain. However, the Obama campaign has failed to create any broad narrative against McCain comparable to McCain’s narrative against Obama (shallow celebrity candidate who’s not ready to lead).

Things may be changing. Last Thursday the Obama team moved quickly to capitalize on McCain’s inability to state how many houses he owns. Within hours, they had this ad up on national cable television. On Friday, they hit McCain again on the same theme with a second ad portraying him as a “country-club” Republican who can’t even remember how many houses he owns:

These ads are a good start, but we won’t be able to milk the house gaffe forever. We need to use other issues and statements to build on key narratives against McCain: he’s out of touch, he offers the same failed policies as George Bush, he’s a hothead we can’t trust with his finger on the button, he’ll say anything to get elected.

If we are lucky, McCain’s future comments or vice-presidential selection will reinforce one or more of these narratives against him. Two years ago, Virginia Senator George Allen fueled further coverage of himself as racially insensitive when, two weeks after calling a dark-skinned activist “macaca,” he lied about whether he had ever used a racial epithet to refer to black people.

However, the Obama campaign can’t count on McCain doing their work for them. The Democratic nominee doesn’t have to deliver this message himself, but I want surrogates from Joe Biden on down to stay on point.

Another strategy is to use ordinary people to portray McCain as out of touch. This ad that ran in Indiana earlier this month is a good start. It contrast McCain’s statements about the economy being strong with comments from average folks in Indiana, Ohio and Kentucky about tough economic times.

As I watch the proceedings in Denver from afar, one thing I’ll be looking for is a sign that the Obama campaign is building an effective case against McCain.

UPDATE: Just saw over at MyDD that the Obama campaign is launching this new national ad today. It makes fun of McCain for not knowing much about the economy and “singing the same tune” as Bush:

Not sure whether the humor works in this ad–what do you think?