It is an inescapable truth of adult life that our choices have consequences. Each of us must live with the consequences of the choices we make. Each of us, that is, except Sen. Joe Lieberman of Connecticut.

Mark Shields

Mark Shields

The Senate Democratic caucus, with which Lieberman regularly meets and which has rewarded him with the chairmanship of the Senate Committee on Homeland Security, reportedly wants to make nice with Lieberman, who basically kicked the Democrats and the Democratic president-elect in the teeth by endorsing Republican John McCain for president last December.

He then spent the next year playing an inseparable Tonto to McCain’s Lone Ranger, including a prime-time speech at the Republican National Convention in St. Paul, Minn., where he all but canonized McCain while openly criticizing Barack Obama.

During the campaign, while introducing the GOP nominee to a Pennsylvania rally, Lieberman called the 2008 election a choice “between one candidate, John McCain, who has always put country first, worked across party lines to get things done, and one who has not.”

In a televised interview while conceding that Obama had labeled Hamas a terrorist organization, Lieberman added: “But the fact that the spokesperson for Hamas would say they would welcome the election of Sen. Obama really does raise the question why. And it suggests the difference between these two candidates.”

Let’s get this straight: The difference between the Democrat and the Republican presidential nominees in 2008, according to the man whom the Democratic Party in 2000 honored with its vice presidential nomination, is “explained” by an unnamed flak for Hamas? Does anyone hear echoes of the late, unlamented Joseph McCarthy in that argument?

Speaking of the 2000 campaign, Lieberman, as a Democratic vice presidential candidate, was much less aggressive and decidedly more gentle in his criticism of his Republican opponents, George W. Bush and Dick Cheney, than he was in 2008 in his public censuring of Obama.

In fact, in the 2000 vice presidential debate, Lieberman disappointed Democrats by failing to even mention the facts that Cheney had been one of only 10 House members to vote against Head Start and one of four in the House to vote against banning plastic guns from airplanes, and even had voted against a congressional resolution calling for the release of Nelson Mandela from captivity.

Lieberman is not the first member of the Democratic caucus to endorse the presidential opponent of the other party. In 1964, Mississippi Rep. John Bell Williams, a Democrat and an all-out foe of federal civil rights laws, endorsed Republican presidential nominee Barry Goldwater. Rep. Albert Watson, a South Carolina Democrat, did the same thing. Mississippi and South Carolina were among two of the six states Goldwater carried that year. When House Democrats convened in January, however, they abided the maxim that choices do have consequences, and Williams and Watson were stripped of their seniority in the House.

The question now before the Senate Democratic caucus is: Do Senate Democrats in 2008 still believe that choices have consequences? If so, Lieberman will be removed from his committee chairmanship. This is not personal. Lieberman has many admirable qualities and is, frankly, likeable. But to ignore his blatant betrayal of the Democratic presidential nominee — especially when elected Democrats in more marginal states and districts put themselves at some political risk by openly backing Obama-Biden — would be to punish those Senate colleagues, junior to Lieberman, who were faithful. It would sabotage party cohesion on Capitol Hill — forget about any party discipline.

Democrats soon will find out that their choices do have consequences.

Mark Shields is one of the most widely recognized political commentators in the United States. The former Washington Post editorial columnist appears regularly on CNN, on public television and on radio. Click here to contact him.