Senator Lieberman weighs in

in the pages of WSJ:

activists have successfully pulled the Democratic Party further to the left than it has been at any point in the last 20 years.

Far too many Democratic leaders have kowtowed to these opinions rather than challenging them. That unfortunately includes Barack Obama, who, contrary to his rhetorical invocations of bipartisan change, has not been willing to stand up to his party's left wing on a single significant national security or international economic issue in this campaign.
[...]
what Mr. Obama has proposed is not selective engagement, but a blanket policy of meeting personally as president, without preconditions, in his first year in office, with the leaders of the most vicious, anti-American regimes on the planet.

Mr. Obama has said that in proposing this, he is following in the footsteps of Reagan and JFK. But Kennedy never met with Castro, and Reagan never met with Khomeini. And can anyone imagine Presidents Kennedy or Reagan sitting down unconditionally with Ahmadinejad or Chavez? I certainly cannot.

If a president ever embraced our worst enemies in this way, he would strengthen them and undermine our most steadfast allies.

A great Democratic secretary of state, Dean Acheson, once warned

"no people in history have ever survived, who thought they could protect their freedom by making themselves inoffensive to their enemies."

This is a lesson that today's Democratic Party leaders need to relearn.