Ellsberg uses the old "lesser than two evils" argument when he asks those voters to support a war criminal who won't be as "bad" as his opponent. As it turns out, Ellsberg is hard put to make a convincing case.
Listen to his description of Obama: "a tool of Wall Street, a man who's decriminalized torture and is still complicit in it, a drone assassin, someone who's launched an unconstitutional war, supports kidnapping and indefinite detention without trial, and has prosecuted more whistle-blowers like myself than all previous presidents put together." 
And Ellsberg doesn't include Obama's use of a "kill" list, violation of human rights here and abroad, increased surveillance of American citizens, token steps toward confronting climate change, and callous disregard for people struggling with foreclosures and economic hard times.
It is hard to see how anybody could be worse!
In fact, Ellsberg recognizes that Romney would not change anything he ascribes to Obama. However, it is curious, indeed, that he reserves for Romney the "attacking Iran" charge when Obama has already put in place all the components for bombing Iran back to the Stone Age. Just because Obama has muted saber rattling during the campaign doesn't mean this war is off his table. Does Ellsberg ignore this because he doesn't want to make it clear that a vote for either Obama or Romney will be a vote for war?
Ellsberg also chalks up "Supreme Court appointments, the economy, women's reproductive rights, health coverage, safety net, climate change, green energy, and the environment" as matters on Romney's "bad" list. Ellsberg overlooks the fact that any of Romney's proposals on these issues would have to pass congressional muster. He does admit that if the Democrats were freed from having the Obama albatross around their necks, they would be more likely to oppose Republican initiatives.
Dr. John Moffett, an editor at OpEdNews and a neuroscience researcher, offers a fuller explanation of this situation: "A major problem with having a Democratic President who governs like a conservative is that Democrats in Congress cannot oppose harmful policies that the White House and congressional Republicans support. President Obama has worked closely with Wall Street, lobbyists, and multinational corporations to help Republicans implement conservative legislation which has essentially crippled any potential Democratic opposition from the remaining liberal and moderate Democrats. So now when President Obama proposes opening up the Arctic and other sensitive marine ecosystems to more oil and gas drilling, despite the BP oil spill disaster, it is virtually impossible for moderate and liberal Democrats in Congress to do anything other than concede. The oil companies and their lobbyists want it, the Republicans want it and the Democratic President wants it, so it becomes very easy for Democrats to do the wrong thing in order to avoid a fight with the oil lobby and their own leader" As long as President Obama is in office progressive causes will be non-starters." 
Furthermore, Ellsberg seems to forget that pronouncements made during this campaign are meaningless. Both men work for the same bosses and, consequently, in the competition to win on November 6th will say whatever they believe voters want to hear.