Why aren't 2nd term presidents popular?

Megan McCardle asks. Of course, notpresidents aren't all that popular either. It's like playing poker. You've got to put together a hand that wins you the office. Recently this has been harder for a Republican candidate though Bush drew into a straight almost busted by his past alcoholism in light of Clinton's misbehavior and our desire for propriety. What might be considered an anti-Republican constraint affected Bush later in the game though in that he effectively was told he had to sell a casus belli on Iraq to the U.N.; so he emphasized the likelihood of present WMD in Iraq. Ever after, 'he lied;' actually he presented his best evidence at the time about which there was rough consensus, kind of like global warming now; and he was probably more concerned about future dangers. Hubris plays a role. It may be that of the American people who can demand that other people not idealize communists as Eisenhower and Dulles and Kennedy, following through the presidential door, did in VN. Or it can be that of a man such as Nixon, who, perhaps following the example of predecessors, breaks'little laws,' but, in his case, wants meticulous evidence of what he did. Obama plays his cards by not leaving 'one scintilla of evidence' which satisfies his partisans completely. Others not so much.