Congratulations, Marco Rubio and Hillary Clinton — you’ve won the endorsement of the Des Moines Register! But what does that mean for your respective campaigns? It’s definitely a good thing. Well, it’ll help … a little … probably.
Let’s look at how past candidates were doing in the polls before getting the Iowa paper’s endorsement and how they did once all the votes were counted. (I’ve updated my colleague Nate Silver’s table from late 2011.) Here’s how the nine Des Moines Register-approved candidates since 1988 fared in the caucuses versus their prior projected vote totals according to the polls:
| YEAR | PARTY | CANDIDATE | PROJECTED VOTE SHARE BEFORE ENDORSEMENT | ACTUAL VOTE | CHANGE |
|---|---|---|---|---|---|
| 1988 | D | Paul Simon | 19.0% | 24.4% | 5.4 |
| 1988 | R | Bob Dole | 36.6 | 37.4 | 0.8 |
| 1996 | R | Bob Dole | 31.3 | 26.0 | -5.3 |
| 2000 | D | Bill Bradley | 31.5 | 35.0 | 3.5 |
| 2000 | R | George W. Bush | 49.8 | 41.0 | -8.8 |
| 2004 | D | John Edwards | 13.0 | 32.6 | 19.6 |
| 2008 | D | Hillary Clinton | 29.3 | 30.4 | 1.1 |
| 2008 | R | John McCain | 6.3 | 13.1 | 6.8 |
| 2012 | R | Mitt Romney | 20.2 | 24.5 | 4.3 |
| Average | 26.3 | 29.4 | 3.0 |
Seven of the nine candidates did, in fact, do better than we expected them to do before getting the paper’s endorsement. This includes the most recent four candidates to receive the paper’s seal of approval.
The paper’s endorsement is credited for greatly improving the fortunes of 2004 Iowa runner-up John Edwards, but most of these candidates haven’t gotten anything like the Edwards bounce. The average post-endorsement bump has been a statistically insignificant 3 percentage points. That’s less than the 8-percentage-point bounce candidates have earned in New Hampshire after locking up an endorsement from the New Hampshire Union Leader. We can also see that both Bob Dole in 1996 and George W. Bush in 2000 lost more than 5 percentage points after being endorsed by the Des Moines Register.
That’s not to say the paper’s endorsement is meaningless. For one, it may hold more sway for Democrats than for Republicans. All four of the Democrats who have gotten the endorsement have done better than projected, compared with three of the five Republicans. And this year it wouldn’t be surprising, for instance, if the Des Moines Register’s decision not to endorse Donald Trump doesn’t affect his fortunes too much given that the paper already called on him to drop out of the race.
The Des Moines Register is the largest paper in the state. Even if newspaper circulations are down and most people aren’t going to be swayed by an editorial page endorsement, it could help drive news coverage for days. Most important, both the Democratic and Republican races right now are very tight. Even though Rubio probably won’t receive enough of a boost to win the Republican caucuses in Iowa, the endorsement could help him finish higher there, in turn helping him in the fight to win the title of “top establishment candidate” in the GOP race. Clinton could be put over the top, however, even if she receives only the 1.1 percentage point bounce she got after the paper’s endorsement of her in 2008.