After blasting Republican colleagues for years over their blockade of President Obama’s agenda, Democrats are gearing up for their turn as the opposition party – planning to throw up early roadblocks for President-elect Donald Trump’s Cabinet picks and proposals.

With the new Congress set to convene Jan. 3 – and Trump set for his inauguration on Jan. 20 – House Democratic Leader Nancy Pelosi last week issued a call to action to her rank and file to fight Republican efforts to repeal and replace the Affordable Care Act, or ObamaCare, one of Republicans’ top agenda priorities for 2017.

Pelosi is planning to intensify the “drumbeat” in the week before the inauguration, setting Jan. 14 as a “national day of action with events across the country.”

The Democrats’ bid to fend off Republican attacks on Obama’s signature domestic policy achievement is no surprise. But the resistance extends well beyond fortifying their ObamaCare defenses.

Bloomberg reports that Democrats are preparing for a separate fight with Republicans over plans to overhaul the tax code.

“There’s going to be opposition if these tax cuts are directed to the people at the top again,” Rep. Richard Neal, D-Mass., the next top Democrat on the tax-writing Ways and Means Committee, told Bloomberg. “We’re going to be pretty united.”

While Democrats have not put forward their own plan, House Republicans and Trump both have outlined overhauls. Both would reduce the number of tax brackets from seven to three, including reducing the top rate for individuals from 39.6 percent to 33 percent. The gist of the plans is to lower tax rates for most people, and make up lost revenue by scaling back exemptions, deductions and credits.

LOBBYING EFFORT IN FULL SWING TO CONFIRM SESSIONS

The House plan, however, retains some of the most popular tax breaks, including those for paying a mortgage, going to college, making charitable contributions and having children.

As Democrats prepare to fight proposed tax breaks for top earners, Senate Majority Leader Mitch McConnell, R-Ky., and House Speaker Paul Ryan, R-Wis., have signaled they may play hardball. Both GOP leaders have said they plan to use a legislative maneuver that would prevent Senate Democrats from using the filibuster to block a tax bill.

Senate Democrats, meanwhile, are signaling a potentially rocky road ahead for some of Trump’s Cabinet picks, last week demanding extensive financial information on some of his wealthy candidates.

Frustrated by the slow response of billionaires and multimillionaires to their request, 16 Democrats delivered an ultimatum Thursday, saying no committee should vote on a nominee until the individual has cleared an FBI background check, provided a financial report and an ethics agreement with the Office of Government Ethics, and responded to "reasonable requests for additional information" such as tax returns.

"The United States Senate has a rich, bipartisan tradition of vetting nominees to the president's Cabinet," said New York Sen. Chuck Schumer, the incoming Democratic leader.

Republicans controlling the Senate want to make quick work of Cabinet confirmations once Trump takes office on Jan. 20.

Democrats have limited options to block nominees outright because they changed filibuster rules when they controlled the Senate in 2013, and Cabinet nominees can win approval on a simple majority vote. Republicans will hold a 52-48 advantage next year. However, Democrats could drag out the process in committee or force longer Senate debates than usual.

Trump's choice of ExxonMobil CEO Rex Tillerson for secretary of state has been a focal point of the complaints. In a letter to colleagues, Maryland Sen. Ben Cardin, the Foreign Relations Committee’s top Democrat, said he asked the Trump transition team for three years' worth of tax returns because Tillerson was "actively engaged with many foreign governments" at ExxonMobil. Cardin said Tillerson "promised to provide" the tax information in response to a question on a standard questionnaire that all nominees submit prior to appearing before the committee.

Tennessee Republican Sen. Bob Corker, the committee chairman, quickly responded with a statement saying the GOP-controlled panel never officially asked for the tax returns and insisted that Tillerson was ahead of schedule in providing information to the committee. He said it is not the practice of his committee to request tax information, and the committee's own financial disclosure forms "are very expansive.”

In addition to Tillerson, Trump has tapped Steve Mnuchin, a former Goldman Sachs executive, for treasury secretary, and Betsy DeVos, daughter of the Amway co-founder, for education secretary.

Trump’s conservative allies outside Capitol Hill are preparing for confirmation turbulence. The Judicial Crisis Network recently launched a website touting the nomination of Sen. Jeff Sessions, R-Ala., for attorney general and defending his record in office.

Former House Speaker Newt Gingrich, a Trump adviser, told Fox News last week that he anticipates congressional Democrats will fall into a few groups as Trump joins with majority Republicans to pursue his agenda.

“You're going to have the hard left -- the Elizabeth Warrens who aren't going to support anybody. They'll be hostile and bitter and nasty. You're going to have the partisan group -- Pelosi is a good example. They are going to be tough-minded,” he said. “But there are going to be a lot of Democrats that are going to say ‘I don't want to deal with eight years of yelling no.’"

The Associated Press contributed to this report.