1)Campaigns don't really matter. Elections are largely decided by the fundamentals of the economy. The graphs in this article would've done more to predict the 2008 election than reading Politico every day.Reporters would be massively better off if they believed this. However, a little complexity never hurts, right?
Let's start with fundamentals. Here's what we know: it's possible to devise a formula to predict presidential general elections that contains only economic information and presidential approval and wind up with pretty accurate predictions. That puts an upper bound on how important campaigns can be -- they can't be much more important than the margin of error in those predictions. And the economy is a major factor in presidential approval.
All that said, there are a few things to be cautious about here. There's more to presidential approval than the economy (Bush's ratings were low before the recession began in December 2007, and of course they were far higher than the economy would have predicted in 2002). Some of the other things that go into presidential approval is beyond the control of the White House, but presidential actions can influence approval. That's outside of campaigns. When it comes to actual campaigns, there's a large literature on whether campaigns matter or not. I believe the prevailing conclusion is that, yes, they can matter a little. Research has found some things that can affect turnout or vote choice, and it's possible for a campaign to get a bit of an advantage by doing those things better than the opposition.
Put it together, and I think the best way to look at it is that there's no way that campaign effects are going to be responsible for any of the blowouts (1964, 1984) or even the solid victories (1980, 1988, 1992, 1996, 2008). Campaign effects may well have tilted the toss-ups (1960, 1968, 1976, 2000). But beware: reporters aren't going to help very much, even there. What usually shows up in Politico-style coverage tends to selectively call whatever the winning side is doing "good" and whatever the losing side is doing "bad." That's a media bias, not analysis.
Now, back up even further. I've been talking about presidential elections, and the general election. I think that's mostly what Ezra was talking about, too. It's worth mentioning, however, that there are lots of elections out there. House (general) elections tend to turn on district composition more than anything else, but differences between voter awareness and perception of candidates turns out to matter a lot, too. And then there are primary elections, where campaigns probably matter quite a bit.
One more thing. By "campaigns don't matter," Ezra is I think talking about the way that campaigns affect voting -- campaigns, he's saying, don't determine which candidate will win. It's worth noting, however, that campaigns have other functions. Candidates take positions on issues of public policy, and then feel constrained once in office by those positions. Of course, candidates break issue promises all the time...but overall, the positions taken during the campaign are a pretty good guide to positions they will take once in office. Had George W. Bush not needed to prove his conservative credentials in order to defeat Steve Forbes, Bush may well have not have campaigned on extreme tax cuts, and not placed such a priority on tax cuts once in office. Had Bush not run in the general election on a platform of "compassionate conservatism," he might not have wound up taken up the issue of education, and then not pushed for NCLB once in office. Another way to put this is that campaigns are about building coalitions, and choices made at that stage have consequences for politicians once they are elected.
More generally, all sorts of non-issue promises are made during campaigns, and Richard Fenno's research shows that politicians are constrained by those promises once in office.
On yet another level, campaigns are also the source of many of the people who make up a presidential administration (or a Congressional staff). Since those people can affect what elected officials actually do, campaigns matter in that way as well.
Again, this isn't meant to be critical of Ezra's list. We'd get much better reporting if journalists suddenly believed that campaigns didn't matter, instead of acting as if every tiny bit of spin and every debate line and whether the balloon fall looks nice at the conventions are the main determinants of who wins the election. Just adding a little complexity.