If Sen. John Kerry does vacate his seat for a job in Barack Obama's administration, Massachusetts will hold a special election for the seat with somewhat complicated rules which would require candidates, parties and election officials to scramble.

According to the secretary of state's office, Massachusetts General Law says that as soon as a sitting senator submits his or her letter of resignation, the governor shall immediately call for a special election within 145 and 160 days from the resignation. The secretary of state will then draw up a calendar of election deadlines - when signatures must be submitted, when the primary will occur - working back from the special election date.

The most recent special election occurred in 2007 for then-U.S. Rep. Martin Meehan's seat. In that race, the governor set the date of the special election for Oct. 16. The primaries in that race were then set by the secretary of state on Sept. 4, six weeks before Election Day. Signatures for the primary in that race were due seven weeks before that, on July 17.

In a U.S. Senate special election, candidates would be required to submit 10,000 signatures from voters of their party and unenrolled voters, according to the secretary of state's office.

If the senator's resignation takes effect before the special election, the governor cannot appoint someone to fill the seat in the interim; the seat would remain vacant until the election.

Fundraising rules also present interesting challenges for candidates. Candidates with an existing account with the Federal Election Commission could use all of the money in that account, according to the FEC. Candidates cannot use funds from their state campaign coffers, nor can they transfer that money into a federal account.

Candidates that only have state bank accounts may, however, refund contributions to their donors and ask them to re-contribute to a federal campaign account, according to the FEC.

Another question is whether those candidates with state bank accounts could use those funds to conduct a poll to test the waters for a run. According to the FEC, if that candidate did decide to run after the poll, he or should would be required to disclose that expenditure and it would have to be paid for by a federal account.

Note: Stay tuned for more on who might run for a U.S. Senate seat later in the day.