President-elect Donald Trump and House Speaker Paul D. Ryan meet in the speaker's office in November. Ryan says their discussions have centered on “a timeline” for passing already- determined Republican priorities. (Alex Brandon/AP)

For six years, since they took back the House of Representatives, Republicans have added to a pile of legislation that moldered outside the White House. In their thwarted agenda, financial regulations were to be unspooled. Business taxes were to be slashed. Planned Parenthood would be stripped of federal funds. The ­Affordable Care Act was teed up for repeal — dozens of times.

When the 115th Congress begins this week, with Republicans firmly in charge of the House and Senate, much of that legislation will form the basis of the most ambitious conservative policy agenda since the 1920s. And rather than a Democratic president standing in the way, a soon-to-be-inaugurated Donald Trump seems ready to sign much of it into law.

The dynamic reflects just how ready Congress is to push through a conservative makeover of government, and how little Trump’s unpredictable, attention-grabbing style matters to the Republican game plan.

That plan was long in the making.

Almost the entire agenda has already been vetted, promoted and worked over by Republicans and think tanks that look at the White House less for leadership and more for signing ceremonies.

(Peter Stevenson,Julio Negron/The Washington Post)

In 2012, Americans for Tax Reform’s Grover Norquist described the ideal president as “a Republican with enough working digits to handle a pen” and “sign the legislation that has already been prepared.” In 2015, when Senate Republicans used procedural maneuvers to undermine a potential Democratic filibuster and vote to repeal the health-care law, it did not matter that President Obama’s White House stopped them: As the conservative advocacy group Heritage Action put it, the process was “a trial run for 2017, when we will hopefully have a President willing to sign a full repeal bill.”

“What I told our committees a year ago was: Assume you get the White House and Congress,” House Speaker Paul D. Ryan (R-Wis.) told CNBC in a post-election interview last month. “Come 2018, what do you want to have accomplished?” Negotiations with the incoming Trump administration, he said, were mostly “on timeline, on an execution strategy.”

Few presidential candidates have dominated the coverage of an election like Trump did in 2016. In the campaign’s final stretch, Republican candidates often got less attention for their records in Congress than for their positions on Trump’s controversial statements.

The irony, as Democrats realized after the election, was that congressional Republicans were poised to have more influence over the national agenda in 2017 than congressional Democrats did after the 2008 election that put Obama in the White House with his party in control on Capitol Hill.

While the Democratic majority in 2009 was larger than the GOP advantage this year, the Democrats were hamstrung in ways they came to regret.

Responding to the Great Recession, they spent the transition and first month of 2009 on a $831 billion stimulus package, with Obama aides openly hoping that they could pass it with bipartisan supermajorities. Every House Republican and all but three Senate Republicans opposed it, and within 20 days of inauguration, the first tea party protests had broken out against it. Protesters twinned their opposition to the stimulus with opposition to the bank bailouts, which had bipartisan backing.

Since November, Republicans have preempted any problems like this by making no attempt to frame their agenda as bipartisan.

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In his first news conference after the election, Ryan said that voters had delivered a mandate for “unified Republican government.” Eight years earlier, then-House Speaker Nancy Pelosi (D-Calif.) had said only that Americans “voted in large numbers for change” and said the White House would be driving the agenda.

This year’s agenda from House and Senate Republicans has clarity that was often lacking from Trump’s own campaign. Senate Republicans favor using a procedure known as “budget reconciliation,” in which measures can be passed with a simple 51-vote majority rather than a filibuster-proof 60 votes, to tackle the ACA and to undo much of the 2010 Dodd-Frank financial reform.

As part of undoing the financial overhaul law, some GOP leaders have begun planning strategies for how to effectively kill the Consumer Financial Protection Bureau, whether by giving Congress control over its budget or finding cause to replace its director, Richard Cordray, with a weaker board.

“I’d like to repeal the whole thing, period,” Senate Banking Committee Chairman Richard C. Shelby said of Dodd-Frank in a December interview with the Wall Street Journal.

The reconciliation process is also likely to be used to pass tax changes, which both Trump and congressional Republicans want to use to lower rates and end the estate tax.

Republicans also are examining ways to undo many of the regulations and other orders enacted by Obama and his administration, including ones issued in the weeks since Trump’s victory and designed to solidify the Democratic president’s environmental legacy.

GOP leaders have cited the 21-year old Congressional Review Act, which allows Congress to cast simple majority votes of disapproval for regulations, as a way to block anything the administration has ordered since June 2016.

Since its passage, the CRA has been used only once. But in December, the conservative House Freedom Caucus began compiling a list of more than 200 regulations it views as vulnerable to a disapproval vote. They include “burdensome” school lunch standards, tobacco regulations, laws that set higher wages for contractors and elements of the Paris climate-change agreement.

“Talking to some individuals with the Trump transition team, they are taking this extremely serious[ly],” Rep. Mark Meadows (R-N.C.), chairman of the Freedom Caucus, told the Heritage Foundation last month.

Republicans intend to supplement the CRA by enacting a law that would subject any regulation with an economic impact greater than $100 million to a vote of Congress, a change that would have prevented nearly every climate or employment rule change of the Obama years. The measure, called the Regulations From the Executive in Need of Scrutiny Act, or Reins, is a conservative priority that passed the Republican House in 2011, 2013 and 2015 with backing from the U.S. Chamber of Commerce. Republican aides now hope for a vote on Reins in the coming days so it can be sent for Trump’s signature immediately after he is sworn in on Jan. 20.

Some Republican lawmakers also want legislation that would stop courts from deferring to federal agencies’ interpretations of statutes — a practice known as “Chevron deference,” after the 1984 Supreme Court case that went against the energy company — and have them instead defer to Congress.

Little of this was discussed during the presidential campaign, and none has much buy-in from Democrats. Just one rural Democrat in the 115th Congress, Rep. Collin C. Peterson of Minnesota, voted for Reins. But Democrats do not see the next few months playing out for them the way the first half of 2009 played out for Republicans.

“I think there was a unique benefit to Republicans in obstructing the Obama agenda,” said Sen. Chris Murphy (D-Conn.), who served in the House in Obama’s first term and arrived in the Senate in 2013. “In 2008, Obama’s entire premise was built on fixing Washington by ending partisanship. It was dependent on getting two parties to work together. Mitch McConnell figured out quickly that he alone held the keys to success or lack of success.”

Democrats, said Murphy, would oppose Republicans where they can. But they are not in a position to block everything. “Trump pays lip service to bringing people together, but his theme is that ‘only he can fix it,’ ” he said. “That’s about results, not whether Washington is ‘working,’ so there’s not the same political benefit to pure obstruction.”

Instead, Democrats see opportunities on issues on which Trump clashed with his party or where Republicans themselves worry that the party’s position is unpopular. One of them is the Defund Planned Parenthood Act, which sailed through the House in 2015. Last month, when Obama issued an order halting state efforts to defund the group, the legislation’s sponsor, Rep. Diane Black (R-Tenn.), said new “pro-life majorities in Congress” would “not only roll back this latest overreach but also enact new legal protections for these most vulnerable members of our society.”

Trump, who became antiabortion late in life, sent mixed messages about Planned Parenthood, praising its non-abortion work in televised debates. That, say Democrats and abortion rights advocates, suggests a wedge can be shoved between the Republican Congress and the president. “Trump didn’t run on, nor was he elected to act on, attacking reproductive health care,” said Ericka Sackin, a spokeswoman for Planned Parenthood.

There’s less clarity about how to respond on other Republican priorities. Legislation to allow concealed weapons to be carried across state lines, a major goal of the National Rifle Association, was endorsed by Trump and may be hard for red-state Democrats to oppose.

A possible Trump-backed stimulus package intrigued even blue-state Democrats when it was floated in November. Interest waned when, in lieu of detailed spending plans, Trump allies suggested the stimulus would consist of tax breaks.

In the short term, Democrats are focused more on Trump’s Cabinet picks and the looming Supreme Court nomination. In 2009, 59 Democratic senators were occasionally bogged down in getting the 60th vote to confirm lower-level Obama appointees such as Tom Perez as an assistant attorney general at the Justice Department and Harold Koh as a legal adviser at State.

In 2017, thanks to Democrats’ change of the filibuster, Republicans no longer need to get 60 votes for cloture on nominees; they need a simple majority for any administration position or any judicial opening lower than the Supreme Court. This, Democrats admit, will give Republicans more running room and more floor time to pass bills. Shellshocked after being defeated in an election few people expected they could lose, some concede that Trump’s ability to command media attention will make it harder to turn their losing congressional battles into headlines.

They will try. On Jan. 15, Democrats will organize rallies in several states to draw attention to Trump’s campaign pledge to leave Social Security and Medicare untouched — a difference with Republicans like Ryan. And the party’s concurrent fight over who will head the Democratic National Committee has focused, in large part, on how the party can draw attention to the fast-moving Republican Congress and promote its own work, something Hillary Clinton failed to do in the campaign.

“There’s no question we’ll see a greater number of people who are uninsured, more people who are unemployed and more kids getting low test scores,” said Rep. Keith Ellison (D-Minn.), a leading candidate for DNC chairman. “But if we think Trump will create bad conditions and that’ll be enough for Democrats to win, we are absolutely wrong.”