New England proved to be perhaps the most important region for Congressional Democrats in Tuesday’s elections.

Senate Democrats had a banner night overall, led by two key Republican seat pickups in the region that allowed them to expand their current majority.

And New England was a key firewall for House Democrats, who flipped two GOP-held seats in New Hampshire and saw vulnerable incumbents in Massachusetts and Rhode Island hang on.

The defeat of New Hampshire Reps. Frank Guinta and Charles Bass — both of whom were elected in 2010 — means there will be no Republican House Members from New England in the next Congress.

Massachusetts Sen. Scott Brown (R) was the only Senate incumbent to lose on Tuesday. He faced a difficult and expensive battle against Harvard University professor and consumer advocate Elizabeth Warren (D) in a state where the demographics were weighted heavily against him. Warren’s victory in a way avenges 2010 Democratic candidate Martha Coakley’s embarrassing loss to Brown in a special election. Warren will become the first woman to represent Massachusetts in the Senate.

Brown hinted in his concession speech that he’s not done with public service.

“Defeat is only temporary,” he said Tuesday night.

He could look at a gubernatorial bid in two years; current Gov. Deval Patrick has said he will not seek re-election. Or he could try to return to the Senate if there is another special election opening. That’s a possibility if Sen. John Kerry (D) were to be tapped to join the Obama administration.

Elsewhere in the Bay State, embattled Rep. John Tierney (D) pulled off a surprising victory against former state Sen. Richard Tisei (R), a victory few people thought was possible heading into Election Day. Tierney, who was dogged by his wife’s family’s legal problems, pulled out a 1-point win in the Democratic-leaning district.

Attorney Joseph Kennedy III (D) easily won the seat of retiring Rep. Barney Frank (D). His victory means that there will once again be a Kennedy serving in Congress; the grandson of Robert F. Kennedy is the first of his generation to come to Capitol Hill. There has not been a Kennedy in Congress since Rep. Patrick Kennedy (D-R.I.) retired in 2010.

In Maine, former Gov. Angus King (I) won the seat of retiring Sen. Olympia Snowe (R). King is expected to caucus with Democrats, although on Wednesday morning he wouldn’t confirm that.

“Next week is an orientation session. I’m going to be going down, probably this weekend, to Washington and talking to the leadership” on both sides, King told MSNBC. “My goal is to be as independent as I possibly can, but I also want to be effective.”

In neighboring New Hampshire, voters tossed out both House Members for the third time in six years. Bass and Guinta were swept in by the 2010 GOP wave, but neither could hold on in the neutral environment of 2012, with President Barack Obama carrying the state.  

Both lawmakers lost to the candidate they beat two years ago. Former Rep. Carol Shea-Porter (D) won back the 1st district from Guinta, while Ann McLane Kuster defeated Bass in the 2nd district.

New Hampshire is now the first state to boast an all-female Congressional delegation.

Democrats also held the Connecticut Senate seat of retiring Sen. Joe Lieberman (I). Rep. Christopher Murphy defeated former WWE CEO Linda McMahon (R), who spent heavily from her personal fortune on her second attempt in three years to win a Senate race. Over the course of two elections, McMahon shelled out close to $100 million from her personal coffers.

Democrats also held Murphy’s House seat, which saw a competitive race to replace him. Former state Rep. Elizabeth Esty (D) defeated state Sen. Andrew Roraback (R).

In Rhode Island, embattled Democratic Rep. David Cicilline held on to win a second term. The freshman lawmaker was plagued by low poll numbers for most of his first term, and Republicans heavily targeted the district. The ability of Cicilline and Tierney to hold on in Democratic districts boosted the party’s overall expected net seat gain.