The Massachusetts Democratic Party is using freshman Sen. Elizabeth WarrenElizabeth Ann WarrenOvernight Finance: Lawmakers grill Equifax chief over hack | Wells Fargo CEO defends bank's progress | Trump jokes Puerto Rico threw budget 'out of whack' | Mortgage tax fight tests industry clout Michelle Obama is exactly who the Democrats need to win big in 2020 Wells Fargo chief defends bank's progress in tense Senate hearing MORE (D-Mass.) in an email to supporters, warning that a vote for former Sen. Scott Brown (R-Mass.) in the likely upcoming Massachusetts special election is a vote to cancel hers out.

Doug Rubin, one of Warren's top advisers, describes in an email how proud he was to see Warren sworn in to the Senate, but notes that the experience "was also a wake up call."

"That's because the special election that will occur when John KerryJohn Forbes KerryFor the sake of national security, Trump must honor the Iran deal Bernie Sanders’s 1960s worldview makes bad foreign policy DiCaprio: History will ‘vilify’ Trump for not fighting climate change MORE becomes our Secretary of State could allow Scott Brown to return to the U.S. Senate.  And if that happens, his votes will cancel out Elizabeth's and wipe out all the hard work of the last campaign," he writes.

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Rubin goes on to admit that in 2010, during the special election that brought Brown to the Senate, "we were caught sleeping and we can't make that mistake again."

"This time we’re starting early, building a strong coordinated campaign that will make sure we send another great Democrat who will stand up for our values to join Elizabeth in the Senate," he writes.

The email is notable for who it does not mention: Democrats' only announced candidate, Rep. Edward MarkeyEdward (Ed) John MarkeyDems lambaste Trump’s ‘outrageous’ EPA chemical safety pick Dems plan to make gun control an issue in Nevada Dem senator pitches ideas for gun control after shooting MORE (D-Mass.). Markey is so far the only person to announce his intentions to run for Democratic Sen. John Kerry's seat; Kerry was nominated in late December for secretary of State, and isn't expected to face tough opposition in his confirmation. Most other possible candidates for the seat have closed the door on a bid, leaving the last remaining obstacle to Markey's nomination Rep. Stephen Lynch (D-Mass.), who has said he's considering a run but hasn't yet decided.

Brown, too, hasn't yet indicated his intentions, though he's considered the most likely Republican to run.

The state party has a policy against endorsing any one candidate in the primary, so it's unlikely that they'll issue any messaging promoting Markey before he makes it through to the general.

But Massachusetts Democrats have been using Warren as a messaging tool since it became clear a special election was likely, suggesting Brown's reelection would run counter to what they consider the clear will of Massachusetts voters, as evidenced by Warren's win.

"I think the voters here are not going to want to send Brown back to the Senate to cancel out most of Elizabeth's votes," Massachusetts Democratic Party Chairman John Walsh told The Hill last week.

Markey will enter the race, according to a December poll, largely unknown, and lagging Brown by 18 percentage points. 

But both Warren and Brown emerged from the election with high favorability ratings, despite a campaign that occasionally turned nasty. It may be Democrats' best option, at least in the early messaging stages, to spin the upcoming special as a rematch between a Democratic darling and, as they've framed Brown, a tool of the Republican Party.

But Massachusetts Republican Party spokesman Tim Buckley defended Brown, charging that Democrats are worried that their "likely nominee" — Markey — is too weak to run against Brown.

"Scott Brown voted nearly half of the time with Senator Kerry and his bipartisan credentials are well established. This bogus attack shows how concerned the Democrats are that their likely nominee is so weak that they would rather fight the last campaign than the next one," he said in an email to The Hill.

--This post was updated at 1:58 p.m.