This much is simple: Republican Trent Lott says he is resigning from the U.S. Senate seat with five years left on his current six-year term.

Mississippi law makes things complicated from there.

If a senator dies or resigns with more than one year left to serve, the governor will appoint a temporary replacement and set a special election. State election law provides two scenarios for the timing of a special election:

— In a year that has a general state election or congressional elections, such as 2008, the special election will be held on the same date as the regular election.

— In a year without a general state election or congressional elections, the special election will be held within 90 days of when the Senate seat is declared vacant. The governor must declare a vacancy within 10 days. That sets up a maximum 100-day timeline from the time a senator leaves or dies and the time the election is held.

The election date is important as candidates scramble to line up support — and financing — for a race that could cost millions of dollars.

Lott said Monday that he intends to resign by the end of this year, though he said he has not set a date.

“I looked at all the considerations. My decision is conclusively I am going to retire this year,” Lott said during a news conference in Jackson.

Within hours of Lott’s announcement, Gov. Haley Barbour issued a news release saying he will set the special election for Nov. 4, 2008 — the same day as the regular federal election.

The chairman of the Mississippi Democratic Party, Wayne Dowdy, said in his own news release that if Lott resigns during 2007, “we expect the governor to uphold the law and call a special election within 100 days. It is important that Mississippi be represented in Washington by a senator who was elected by the state’s voters as soon as possible.”

Barbour spokesman Pete Smith said the governor’s staff had researched election laws before Barbour issued the statement that the election would be next November.

Mississippi Secretary of State Eric Clark is the state’s chief elections officer. He said there will not be party primaries for a special election.

Smith said the governor’s staff was still conducting research late Monday on when candidates’ filing deadline would be for a Nov. 4 special election.

During a news conference in Jackson, Lott said Barbour had asked him for a recommendation to fill the Senate seat.

“I told him what my preference was, but there are other really good men — and women — that could fill that role on a temporary basis or a permanent one,” Lott said.

Lott would not reveal who he recommended to the governor, although in response to reporters’ questions, Lott praised Mississippi’s two Republican members of Congress, Chip Pickering and Roger Wicker. Each had worked for Lott before being elected to the House.

Two prominent Democrats, former Gov. Ronnie Musgrove and former Attorney General Mike Moore, said Monday that they’re considering running.