One of the things that seems to have become accepted as a truism among the pundit class is that the Democrats ultimately hurt themselves by their opposition to the Vietnam war by appearing as 'soft on defence'.
This meme was mentioned in Dan Balz article that is on the front page and Peter Bienart played it up in anotherwise actually decent interview I heard with him on KGO being interviewed by John Rothman.
No doubt the 'soft on defense' line gave partisan Republicans a reason to oppose the Democrats, but was it really that big an issue at the time?
I certainly would agree that it hurt McGovern in 1972, but the Democrats had little trouble keeping control of the House of Representatives for another 22 years after that election and the Senate for another eight.
I read a book on Jimmy Carter's 1976 presidential win and foreign policy didn't seem to be that big an issue except for Carter benifitting from Gerald Ford's bizarre comment that Eastern Europe wasn't under Soviet domination. Certainly there seemed to be little concern of a little known one term governor from Georgia (which was a much smaller state 30 years ago population wise than it is now) becoming the leader of the
'Free World'.
In 1980, Carter lost. But, what seemed to defeat him was not concern that he was too 'soft on communism' (despite Reagan attacking him for that), but for his inability to handle the Iran hostage situation, as well as the horrible economy and oil prices. In fact, even with the horrible economy and oil prices, Carter likely would have been reelected due to his attack on Reagan as being 'too hard on Communism' (or more precisely: too willing to go to war) had it not been for the hostage situation (the week of the 1980 election was the one year anniversary of the hostage taking).
Beyond that, prior to the Vietnam War (or at least the escalation) Lyndon Johnson crushed Goldwater on concerns that Goldwater would be too likely to go to war (or more specifically, use the atomic bomb).
I've actually been disappointed by the Democratic willingness to use the Iraq war to make the case for the larger narrative: (for partisan Democrats, that Republicans are warmongers), but for the larger audience that Republicans aren't safe for securing the country because they have no ability to use sound judgement to decide when to go to war and when it would not further the interests of the nation.