Political scientists have long puzzled over the veto.  Professional legislators spend considerable time and effort crafting and debating a piece of legislation knowing that obtaining the president’s support is the final hurdle to success.  The president for his part communicates in advance his concerns and objections about the pending legislation.  Often he indicates the revisions that would be necessary to obtain his signature.  So how do we end up in a situation where Congress passes a bill and the president vetoes it?  Why didn’t Congress accede to the president’s demands? If the demands were unacceptable, why not drop the matter all together to work on some legislation that could pass?

Researchers have typically offered two answers.  The first, best developed by my colleague Charles Cameron, is that vetoes are the result of poor information about the president’s preferences and priorities.  Yes, the president may promise to veto a piece of legislation, but he might just be bluffing.  So Congress might be willing to pass the bill in the hopes that president reneges on his threat and signs the bill anyway.  If they guess wrong and he vetoes, Congress does have the chance to override or if that fails pass new legislation that accommodates the president demands. This perspective does explain some important features of “veto bargaining.” In particular, it correctly predicts that many vetoes are followed up by subsequent legislation that is more appealing to the president.

But uncertainty about the president’s preferences seems like a poor explanation for President Obama’s veto of the Keystone Pipeline approval bill.  The president’s veto threat left exceptionally little wiggle room, and there appears to be little chance of overriding the veto.  So if all the Republican Congress cared about was expediting the building of the pipeline, passing the Keystone bill accomplishes very little toward that end.  But a second perspective on veto politics may help to make sense of these events.  Tim Groseclose and I have argued that presidential vetoes should be thought of as instances of “blame-game” politics.  The idea is that Congress often passes legislation that it knows that the president will veto in order to reveal unflattering information about the president’s positions and priorities.  Because polls have consistently shown that voters are generally in favor of the pipeline, the veto engineered by the Republicans places the president on the wrong side of public opinion.  The veto also pays strategic dividends in that it drives a wedge between two of the president’s key allies:  organized labor and the environmental community.  Although the economic benefits and jobs associated with the pipeline may be over hyped, the veto provides a potent talking point that the president is not serious about his “middle class economics” agenda.

While political scientists might not completely agree on the nature of the veto, there are some ideas that don’t have a lot of currency.  For example, the “folk” idea that the veto is a symbol of political strength is a non-starter.  If that were true, Gerald Ford would be on Mount Rushmore.  The veto is the weapon that presidents use when all other defenses have been breached.  President Obama had to veto the Keystone bill because he no longer has a Senate majority to do his dirty work.  Moreover, why would the Republicans send up veto bait just so the president can look presidential?  The evidence shows that Congress is pretty good at this calculation.  Groseclose and I find that presidential approval tends to drop during periods in which the president is issuing the most vetoes.

But perhaps the most interesting thing about the veto is that its usage has been on the decline.  The Keystone veto is only President Obama’s third veto.  George W. Bush vetoed only 12.  By contrast, Bill Clinton and the first President Bush vetoed 37 and 44, respectively.  Of course, the main difference between these presidencies is that George W. Bush and Obama spent most of their presidencies controlling at least one chamber of Congress.  Now that that is no longer the case for President Obama, the veto should reemerge as an important feature of the policy making process.