Democrats can’t do much to block Donald Trump’s Cabinet nominees from Senate approval, but the party is approaching the confirmation process as one of the first steps in its rebuilding effort following painful November losses.

That effort includes getting opposition research and outside messaging groups into high gear, fundraising off of certain confirmation hearing highlights or controversies regarding some nominees, and coming up with a way to paint the administration they will run against in four years in an unflattering light.

That next presidential election isn’t so far off for some Democrats, who see the confirmation hearings as a way to advance their own ambitions. Indeed, one could almost mark January 11, 2017 as the day the 2020 presidential race began: That was the day New Jersey Sen. Cory Booker took the unprecedented opportunity to testify against colleague Jeff Sessions, Trump’s choice for attorney general.

No sitting senator has testified against another in a confirmation hearing -- a historical tidbit Booker isn’t shy about pointing out. While the first-term senator argues that his colleague’s history regarding civil rights, immigration, and voting rights warrant the revolutionary move, others may see it as a way for Booker to build up his bona fides as a party leader -- particularly since Sessions is essentially on a glide path to confirmation.

"I believe, like perhaps all of my colleagues, that in the choice between standing with Senate norms or standing up for what my conscience tells me is best for our country, I will always choose conscience and country," Booker told the Judiciary Committee Wednesday.

The senator's statement could have been read as something of a stump speech. "The arc of the universe does not just naturally curve toward justice – we must bend it," he said in opposing Sessions.

Booker was joined in opposition by civil rights leader and Georgia Congressman John Lewis, along with Rep. Cedric Richmond, the chairman of the Congressional Black Caucus. But the senator's testimony received a different kind of attention, as the party seeks to cultivate its bench of future presidential candidates. Past GOP contenders like Ted Cruz and Rand Paul notably capitalized on the platform the Senate offers -- in the form of floor speeches and hearings -- to gain attention. Few activities there are by accident or coincidence. Booker was spotted last week giving an interview to a prominent New Hampshire television station.

For Democrats especially, the Cabinet hearings serve as a reminder that elections have consequences, as do their own actions. There is little they can do to prevent Trump from assembling his chosen Cabinet, save for some tactical delays, thanks to a 2013 Democratic-sponsored change to Senate rules after continued Republican obstruction against President Obama’s executive appointments. Now, confirmation requires a simple majority vote for nominees, so Republicans will reap the benefits of that alteration, even if their majority is a slim 52-48 margin.

But as they settle into life in the minority in Washington, Democrats have the opportunity “to test-drive the opposition,” says Democratic strategist Jesse Ferguson. “We don’t have to accept the course of the next four years as a foregone conclusion.”

Still, Ferguson cautions that the trick is to oppose Trump’s agenda because “it is the wrong direction for the country, not … merely for the sake of obstructing.”

One area of potential that Democrats see lies in the fight over how and when to repeal and replace the Affordable Care Act, a key legacy item of the outgoing president. Democratic lawmakers take some solace in the knowledge that Republicans have not coalesced around a replacement plan for the law they have wanted to repeal since its inception. And Republicans are largely at odds with the president-elect regarding costly entitlement programs: Most GOP lawmakers want to reform Social Security and Medicare, while Trump has vowed to leave the programs alone. Democrats will likely highlight these divisions during the hearing for Trump’s pick to lead the Health and Human Services, Rep. Tom Price, who is looks poised to be confirmed.

“We will be at our strongest if we have a unified theme that we can carry across issues,” Progressive Change Campaign Committee co-founder Adam Green said on a conference call with Senate Minority Leader Chuck Schumer and other Democratic leaders to discuss Obamacare strategy. “The more unified we can be with our thematic messaging across issues -- as opposed to ad hoc messaging -- the more strategic that will be and the more people will hear our message.”

But on other issues regarding Trump, Democrats aren’t exactly a united front. If Booker represents one aspect of a party in the process of post-election recovery, West Virginia Democratic Sen. Joe Manchin represents another. As does Indiana Sen. Joe Donnelly. And North Dakota’s Heidi Heitkamp. And Montana’s Jon Tester.

All are all up for re-election in 2018 and represent states Trump won overwhelmingly. Democrats will also have to defend Senate seats in states such as Wisconsin, Ohio, and Pennsylvania, which are now technically Trump states. As a result, the midterm map is challenging for Democrats, and Republicans hope to secure a filibuster-proof majority. Trump may get some support from vulnerable Democrats for his Cabinet picks, or his other priorities such as filling the Supreme Court vacancy. Manchin has expressed support for Sessions, for example, and has spoken in person and over the phone with Trump on recent occasions.

Schumer brought Manchin into his leadership circle, partly to deter him from switching parties, along with Bernie Sanders. The Vermont senator, intent on continuing the revolution he sparked during the primary, has been vocal against Republicans on health care, urging Trump to keep his pledge to stay away from entitlement programs. Still, positions in party leadership aren’t likely to deter them from pursuing their own prerogatives. Meanwhile, other lawmakers will be jockeying for positions in the party to advance themselves, particularly since there is no clear frontrunner for the Democratic presidential nomination in 2020.

At 47 and a former Newark mayor, Cory Booker is no stranger to ambition, and has long been talked about as a potential presidential candidate. Some fellow Democrats lauded Booker’s decision to testify against Sessions as a principled move. “If you don't get how much courage @CoryBooker is showing, you don't understand the Senate and how rare this is -- kudos,” tweeted Ron Klain, former chief of staff to Joe Biden.

Republicans, however, were quick to point out Booker’s deviation from his more bipartisan endeavors. “I feel blessed and honored to have partnered with Sen. Sessions in being the Senate sponsors of this important award," Booker said in 2015 of teaming up with his Alabama colleague on legislation, signed by the president, to award the Congressional Gold Medal to those who marched in Selma, Ala., in 1965.

“I’m very disappointed that Senator Booker has chosen to start his 2020 presidential campaign by testifying against Senator Sessions,” wrote Arkansas Republican Sen. Tom Cotton, who visited Iowa last year and is himself considered an eventual presidential candidate. “This hearing simply offers a platform for his presidential aspirations. Senator Booker is better than that, and he knows better.”