In addition to their successful courtship of Sen. Arlen Specter (Pa.), Democrats have tried to bring Sen. Olympia Snowe (Maine) to their side of the aisle, Sen. Barbara BoxerBarbara Levy BoxerHillicon Valley: Ocasio-Cortez clashes with former Dem senator over gig worker bill | Software engineer indicted over Capital One breach | Lawmakers push Amazon to remove unsafe products Ocasio-Cortez blasts former Dem senator for helping Lyft fight gig worker bill Only four Dem senators have endorsed 2020 candidates MORE (D-Calif.) said Wednesday.

Appearing on MSNBC, Boxer was asked if Snowe could be persuaded to join the Democratic caucus the same way Specter was.

"This is something we've done in the past," Boxer responded, "and Olympia will do what she will do. You don't twist someone's army to come over; I don't really believe that."

Snowe has found herself in the national spotlight again as one of the few moderate Republicans left in the Senate after Specter's defection. Snowe also penned an op-ed in the New York Times on Wednesday on how difficult it has become to be a moderate in the GOP.

On Specter's decision, Snowe wrote: "The political environment that has made it inhospitable for a moderate Republican in Pennsylvania is a microcosm of a deeper, more pervasive problem that places our party in jeopardy nationwide."

"I have said that, without question, we cannot prevail as a party without conservatives," Snowe also wrote. "But it is equally certain we cannot prevail in the future without moderates."

Boxer, on MSNBC, said she doesn't see where Snowe, and other moderates like Sen. Susan Collins (R-Maine), fit in the GOP anymore.

"I just don't see that there's a future for someone who is pro-choice, like she is, in the Republican Party, pro-environment, like she is," Boxer said. "I just don't think she's the right fit for them anymore, but this will be her decision, for sure."