Michael Tomasky wants us to believe that Powell’s Obama endorsement is significant:

Ask yourself this. Is there really anyone out there in America who would listen to Ross Perot who was thinking of voting for Obama and will switch to Romney? No. There is no Perot/Obama crossover audience. But are there people out there who are still undecided but for whom Colin Powell’s view would be something they’d take into consideration? Of course there are. Many many thousands of them.

As a general rule, endorsements don’t matter very much. The endorsements of has-been presidential candidates and former Secretaries of State are even less important. There might be some former Perot voters that supported Obama in 2008, but I doubt that Perot’s endorsement of Romney matters to them. Powell has a high favorability rating, as former and current Secretaries of State tend to do for some reason, but I doubt there are any otherwise Republican-leaning and undecided voters that will be swayed by what Powell said. There are many moderate Republicans and independents that will prefer Obama to Romney, but it’s likely that they have been supporting Obama for most of the year. Powell’s endorsement won’t be a cause of moderate Republican and independent support for Obama. It is a reflection of weak support for the Republican ticket among moderates. The voters most likely to take Powell’s endorsement into consideration are also probably the ones that were going to support Obama anyway.

Besides, it’s not as if Powell’s endorsement comes as a surprise. On foreign policy alone, Romney has gone out of his way to make himself unacceptable to someone like Powell, and there are enough other disagreements on domestic policy that it would have always been a stretch for him to justify backing Romney. If he were going to endorse Romney, he presumably would have done so on foreign policy and national security grounds, and Romney’s campaign this year made it impossible for him to do that. Voters that would take Powell’s criticism of Romney’s foreign policy seriously have already reached a judgment about Romney’s readiness to be president, and I suspect the vast majority of them already reached the same conclusion Powell did. The endorsement is an indication of Powell’s ongoing alienation from his party, but other than that it just isn’t that important.