On Election Day, there will be 34 Senate seats up for grabs, while all 435 seats in the House of Representatives will be on the line -- some more heavily in doubt than others. On the state and local level, careers will be launched, while legacy-defining decisions will fall in the laps of fresh-faced mayors and city council members.
Here is a look ahead at a group of the movers and shakers who aren't running for the White House -- some of them familiar, while others are only beginning to rise to prominence -- who figure to make themselves known in 2016.
Seattle City Councilor Kshama Sawant won a bitter, expensive reelection fight in 2015, cementing her place as a power player in this increasingly progressive metropolis.
"We have shown that not only can a socialist win in the US, a socialist can drive the political agenda of a major city," Sawant wrote in a recent editorial for the Guardian.
In the coming year, the Socialist Alternative Party member will work alongside her fellow council members to implement the city's first-in-the-nation "democracy voucher" campaign finance reform plan.
A second act for the Senate's liberal golden boy?
Before Elizabeth Warren had a "wing" or anyone felt "the Bern," former Wisconsin Sen. Russ Feingold was the Democrats' great liberal hope. He even worked across the aisle with Sen. John McCain to author (and pass!) major campaign finance reform legislation, much of which was subsequently wiped out by U.S. Supreme Court decisions.
In 2010, Feingold was swept out of office in the tea party wave, replaced by Republican Ron Johnson. But the rematch favors the Democrat, who will likely be boosted by a larger general election turnout, Johnson's declining popularity, and his own party's revved up left flank.
Finally getting her shot
California Attorney General Kamala Harris has been tipped as a rising national figure for years. In 2016, she is poised to deliver. A candidate to replace retiring Sen. Barbara Boxer, Harris, the first woman of woman of color to be elected the state's top cop, will square off with Rep. Loretta Sanchez in the Golden State's "jungle" primary, on June 7. With a swath of lesser-known candidates in the race, the pair are likely to face off again in November, provided they finish as the top two vote-getters. Expect to see a lot of Harris during the party's big 2016 convention showcase in Philadelphia this coming summer.
A moderate to replace Marco
Sen. Marco Rubio decided not to seek another term while running for the Republican presidential nomination, so the race is on fill his seat.
And Rep. David Jolly made early waves in a crowded Republican field when called for Donald Trump to quit the GOP primary.
"His brutal, bullying bigotry runs contrary to the very principles our forefathers fought so hard to defend," Jolly said, after Trump made his infamous call "for a total and complete shutdown of Muslims entering the United States."
As Tampa Bay Times political editor Adam Smith put it a couple days later, "Jolly has done something no one in that Senate primary has managed to date: Be interesting."
What do you see in Lucy?
When Democrats look at former state Rep. Lucy Flores, they see their future leader -- at home and, perhaps, in Washington, D.C. After losing out in the 2014 lieutenant governor's race during a horrible year for the party, Flores is right back up, challenging a sitting Republican in the state's 4th congressional district.
Flores has been a darling in liberal circles for years and her personal story -- she was abandoned by her mother as a child, before joining a gang and dropping out of school -- is certainly moving.
Going into 2014, she also had one very influential friend in Senate minority leader Harry Reid, the longtime Nevada powerhouse. Reid had high hopes for her in 2014, when he told reporters, "Demographically, she's perfect: Young, dynamic, Hispanic."
But this year's a different story -- Reid dropped Flores to endorse one of her primary rivals, state Sen. Ruben Kihuen, in September.
Lowered a flag, raised her profile
South Carolina Gov. Nikki Haley's name has been bandied about as a potential 2016 Republican vice presidential candidate for years -- and if that's what she wants, her performance in 2015 could have put her that much closer.
Following the shooting deaths of nine black parishioners by a white man in a Charleston church this past summer, and the subsequent campaign to remove the Confederate battle flag from the state capitol grounds, Haley deftly managed to keep the political peace.
As the flag came down -- with the governor's backing -- in July, her viability as a broadly appealing national figure shot up.
California is betting on her
State Controller Betty Yee is a Democrat, but in 2015 she broke the party line and pushed for tax reform that would reduce the burden on the wealthy, while increasing social welfare spending. Which is to say, she's not playing for cheap political points.
Years earlier, in 2011, she emerged as a strong advocate for a new online transaction tax, which was vigorously opposed by Amazon. Then a member of the state Board of Equalization, where she was twice chairwoman, Yee and her allies prevailed and the Amazon Tax was eventually passed, surviving a challenge in the Supreme Court it is still in effect today.
With California's budget woes a perennial sore spot for both parties, Yee's reform plans could signal the beginning of bigger and brighter personal ambitions.
2016 could be A-OK for Granger
Kay Granger, the Republican congresswoman from the 12th district of Texas, has been on Capitol Hill for nearly two decades, but she is closing in on a bit of history in 2016. The current chair of the House Subcommittee for Foreign Aid, Granger is expected to be in the running to take over the top job at the high-powered Appropriations Committee, which gets a big say in the fate of every federal tax dollar.
If Granger gets the nod, she would become the first woman to chair a major league House committee.
Mr. Mosby's neighborhood?
Baltimore will elect a new mayor in 2016, as its current boss, Stephanie Rawlings-Blake, steps aside after tumultuous reign. Enter city councilor Nick Mosby, a Democrat who famously described the riots following the death in police custody of Freddie Gray as a plea for help from the city's "hopeless children."
Mosby enters this fraught race as the second best-known person in his own household. His wife, Baltimore City's State's Attorney Marilyn Mosby, brought the charges against the officers allegedly responsible for Gray's death.
Politically, Mosby's personal life could be a blessing or curse. In either event, he's going to have a very interesting 2016.