With speculation running rampant that New Hampshire Republican Judd Gregg could be plucked from the Senate by President Obama and nominated to serve as Commerce Secretary, we return again to the ugly question of how some senators are selected rather than elected.

Indeed, talk that Gregg might be negotiating to define the political pedigree of his successor sums of the problem with letting governors make appointments to fill Senate vacancies.

Gregg is the scion of an old Republican family in New Hampshire and, while there are indications that he is interested in the Cabinet post, he is reportedly uncomfortable with the notion that his exit from the Senate might permit the Granite State’s Democratic governor to make a partisan switch.

Gregg apparently wants the Cabinet post. But he there have been indications that he might not take it unless he gets an agreement that New Hampshire Governor John Lynch would appoint a Republican to fill the Senate seat he would vacate.

This is all a very big deal not merely for Gregg but for the Senate’s Democratic and Republican caucuses and the Obama White House, as Democrats are now agonizingly close to establishing a filibuster-proof majority in the chamber.

Currently, 58 senators caucus as Democrats. One seat — that of former Minnesota Senator Norm Coleman – is currently open. Democrat Al Franken leads Republican Coleman in the ballot count from Minnesota, and is likely to be seated eventually. That would bring the Democratic caucus to within one seat of the super-majority that is needed to prevent filibusters and to advance major appointments and policy measures – such as Obama’s economic stimulus plan – without having to compromise with Republicans.

If Gregg were to leave, and if Lynch were to appoint a Democrat, the “magic” number of 60 would be within reach for Senate Democrats. If Gregg, who is likely to face a tough 2010 reelection race in a state that is trending Democratic, could be convinced to quit without strings attached, Democrats could gain the advantage.

If Gregg, arguing that the Obama administration needs a Republican with good ties to his party’s Senate caucus in the Commerce position, Republicans would come out ahead.

All of these calculations are in play.

And all of them are inappropriate in a country that is supposed to have an elected Senate.

Senate seats should not be the subject of these sorts of calculations, which are only slightly less crass than those in which former Illinois Governor Rod Blagojevich so famously engaged – and which may actually be more serious in their potential consequences.

A loophole in the 17th amendment – which was enacted with the purpose of creating a directly-elected Senate — allows vacant seats to be filled by gubernatorial appointments that are supposed to be “temporary” but that frequently extend for several years or longer. This loophole should be closed, as Wisconsin Senator Russ Feingold proposes in a newly-offered Constitutional amendment that would require special elections to fill vacancies – as is the case when House seats open up before the end of a member’s term.

But Constitutional amendments take time to pass.

What should be done now? First off, everyone involved needs to recognize that senators should not be allowed to negotiate over the partisan allegiances of their successors. If Gregg is unwilling to give up his seat without strings, he should remain in the Senate. By the same token, it is unsettling to think that a senator’s resignation might make it possible for a governor to significantly alter the partisan state of play in Washington.

One option would be for New Hampshire to take steps to hold a special election, as was proposed in Illinois. A number of states – including Rhode Island and Maryland – are currently considering such moves.

If there are legal or state constitutional barriers to quickly making this shift in New Hampshire, Lynch and legislators there could do what some states did before the passage of the 17th amendment. In the early years of the 20th century, when senators were still selected by state legislators, a handful of progressive states organized “advisory elections,” in which candidates campaigned and voters cast ballots. Once the ballots were counted, the legislature would take the advice of the voters and name the winner to the Senate.

If Gregg goes, New Hampshire can and should strike a blow for democracy by assuring that his replacement is the popular choice of the electorate, rather than the appointee of one man who happened to be governor.