(CNN) – June 25 marks the "probable" date for the special election to replace Democratic Sen. John Kerry, William F. Galvin, the Massachusetts secretary of the commonwealth, told CNN Monday.
As the president's pick for U.S. secretary of state, Kerry sailed through his confirmation hearings last week and is expected to be confirmed as early as Tuesday. Should he submit his resignation this week, "that will set the clock going," Galvin said, referring to the Massachusetts law that stipulates a special election must occur 145-160 days after the seat becomes vacant.
That pushes the time window to late June or early July, but Galvin said all parties involved want to avoid a July election, right in the thick of summer vacation.
He added he was hoping for an election on June 18, when most schools are still in session. However, that's no longer an option, as it would fall before the 145-day mark.
And while summer will have already started for many on June 25, the late-June date is still more ideal than the following week, he said.
"We all agree we don't want to have an election right before the weekend of the Fourth of July," he said.
It's ultimately up to Gov. Deval Patrick, a fellow Democrat, to set the dates.
"I'm hoping the governor will make a decision this week, and I expect he will," Galvin said, though stressing anything can happen.
After the election is officially announced, candidates have four weeks to collect the required 10,000 signatures in order to get on the ballot. Galvin said he recommends the primary take place on April 30.
Until the seat is filled later this year, Patrick will appoint an interim senator. Retired Rep. Barney Frank, who recently left Congress after his term ended earlier this month, has expressed interest in the short-term position.
Longtime Democratic Rep. Ed Markey, the only announced candidate for the special election, launched his campaign last month and already has strong backing from Democratic forces–including the Democratic Senatorial Campaign Committee, Ted Kennedy's widow Vicki, and Kerry, himself. Rep. Stephen Lynch, another Democrat, is still weighing his decision to enter the race.
On the Republican side, former Sen. Scott Brown, who lost his seat to Sen. Elizabeth Warren in November, may make another attempt at the U.S. Senate. A source close to the Bay State Republican told CNN recently that "Scott is undecided. I think he's going to wait for an actual vacancy to be declared and for an election date to be set."
While Markey doesn't yet have an opponent in the race, he called on his potential foes to keep outside money away from the race, a similar pledge made by Warren and Brown last year in their high-profile Senate showdown. The two candidates vowed to deduct money from their own campaigns if a third party group, such as a super PAC, spends money in the race.
"If all the candidates agree, we can give the voters the kind of debate they deserve. This election should be a forum for the voices of everyday voters, not attacks from Karl Rove and other outside special interests," Markey said in a statement.
The 2010 Supreme Court decision, known as Citizens United, paved the way for groups to spend unlimited amounts of money on a candidate, as long as the groups don't coordinate with the campaigns they support.
"This election should be focused on big issues and ideas, not big-money outside groups," Markey said. "I urge all candidates to join me in ensuring that Massachusetts once again will be the leader for the nation on this issue."
– CNN Political Editor Paul Steinhauser contributed to this report.