Clarification/Follow-up by rhonacristyl on 10/23/03 9:56 pm:
Raiden936, as you may have noticed many experts have also clarified that the choice of US senatorial replacement is not necessarily dependent on the political party the resigning senator belongs to, but more about what the particular state government (may it be through their governor or legislature) wants, as seen in the US Constitution's 17th Amendment (w/c I should have reviewed more thoroughly first before giving my case study-oriented answer, I must humbly admit!):

*This was copied & pasted from the US Senate's official website*

The 17th Amendment to the U.S. Constitution:

The Senate of the United States shall be composed of two Senators from each State, elected by the people thereof, for six years; and each Senator shall have one vote. The electors in each State shall have the qualifications requisite for electors of the most numerous branch of the State legislatures.

When vacancies happen in the representation of any State in the Senate, the executive authority of such State shall issue writs of election to fill such vacancies: Provided, That the legislature of any State may empower the executive thereof to make temporary appointments until the people fill the vacancies by election as the legislature may direct.

This amendment shall not be so construed as to affect the election or term of any Senator chosen before it becomes valid as part of the Constitution.

. . . If anything, this respect for the state executive office and legislature in replacement decisions is reflective/reminiscent of the fact that before 1913, US Senators were not popularly/directly elected by ordinary citizen voters, but actually elected by individual state legislatures.

Also, elgin_republicans also gave an insightful private answer to me about the practice of senatorial replacements, w/c I now also share w/ you:

It would depend on the specific wording of the statutes of a particular state. There may be wording that says the appointment must be of the same political party as the former Senator - BUT in most of the states, the Governor is given authority to appoint whomever he/she wants.

In a couple of cases, the sitting Governor appointed himself. There have been a couple of instances when the wife of the former Senator was appointed (most recently in Missouri with Carnahan).

The questions about continuing representation is not even on the list of considerations. Hence, the only questions that are important are: what appointment will most benefit me, my party, my legacy, my re-election, my whatever. You may use "our" for "me" if the Governor is more concerned with his Party than his personal fortune.

. . . Remembering again the transition JFK made from US Senator to US President, it also helps to know that Massachusetts' incumbent governor during that 1960 election year was his fellow Democrat, their state's first Italian-American governor, Foster Furcolo.

Though Furcolo was practically a lame duck after the 1960 election because by then another Italian-American - but a Republican one, being an Eisenhower protege - John Anthony Volpe became the Massachusetts Governor-Elect, Furcolo still wisely used his remaining time in power before Volpe's swearing-in to get fellow Democrat Benjamin A. Smith II appointed as JFK's US Senate replacement, w/c gave JFK's rather narrowly-won mandate one more friendly Senate vote to count on, as well as non-threateningly warming that seat for JFK's own brother Ted Kennedy to win later on in 1962.

Things would have probably been rather different if a Republican happened to be the incumbent Massachusetts Governor during JFK's resignation, who knows . . .

Indeed, w/ the rather self-serving/dynastic/party-centric (when possible, that is) machinations that have usually popped up during US Senate resignations or vacancies, things can get quite interesting as to how the decisions stemming from a particular state government (regardless of party affiliation) can affect an entire nation down the line.

Case in point: it will be interesting to see what will happen if the Democratic US Senator from New York Hilary Clinton does win the US Presidency at a time when a Republican like current New York Governor George Pataki is still in office.

Pataki might just appoint a fellow Republican to Hilary's seat (this might even be more likely if New York's state legislature happens to be under a Republican majority at that same time too), and if it happens that the US Senate at that period happens to be in a susceptible "swing vote" mode, the appointment into the US Senate of one more solid Republican - ironically from the seat & home state of a Democrat President, serving out the remainder of the original term - may spell the difference between the incoming administration initiatives either being smoothly passed or constantly railroaded.

Thank you fellow experts for clarifying for us all the procedures behind US Senate replacements and tactfully reminding me at least of the 17th Amendment, and thank you Raiden936 for the thought-provoking question :-)