A Republican-dominated Congress convenes on Tuesday with a carefully crafted plan to erase much of what the Obama administration considered to be its main domestic achievements, starting with healthcare and environmental regulations.

Barack Obama is seeking to rally Democrats on Capitol Hill on Wednesday for a rearguard struggle to salvage at least some of his signature legislation in the face of looming attacks over the course of the incoming Trump administration. But the party’s ability to resist is hampered by Republican legislative tactics designed to minimize the power of the minority, and by the fact that 10 Democratic senators will face re-election two years from now in states won by Donald Trump, making them reluctant to defy him.

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In light of such handicaps, Democrats are likely to focus their limited political resources on fighting the confirmation of Trump nominees for high office, particularly in the supreme court, and to join forces with Republican senators pushing for a thorough investigation of the Russian role in the presidential election.

Republican leaders in the House and Senate have signalled that their first target in the 115th Congress will be the Affordable Care Act (ACA), widely known as Obamacare, and have made clear they will not wait for Trump’s inauguration to start dismantling it.

“Repeal and replace” legislation has been developed since the ACA came into place in 2010, awaiting the arrival of a sympathetic president. The Democrats’ last line of defense is in the Senate, where they control 48 of the 100 seats, including two independents who normally vote with them. That gives them the power to hold up major legislation through filibusters that would require 60 votes to overcome. So the Republicans’ plan to start unraveling Obamacare from their first day back at work is based on the use of budget measures that require only a simple 51-vote majority, and new procedural rules that ease budget constraints on their actions.

The main obstacle to the destruction of the ACA is not the Democrats, but the sheer complexity of unpicking its provisions, which offer tax credits for purchasing private health insurance and allow states to expand coverage of Medicaid, a longstanding program for low-income Americans. It may be politically necessary to replace those provisions with other forms of healthcare coverage, but House and Senate Republicans are divided on how to do that, and on the overall ambitions of their healthcare counter-revolution.

Many in the House want to use Republican dominance of government to rewrite the Medicare program for the elderly that dates back to Lyndon Johnson, but there is less enthusiasm for that in the Senate. The likely outcome of such complications is that the effective date for Obamacare repeal and replacement will be deferred for several years.

The other priority for the Republican majority in the first days of the new Congress will be a planned bonfire of Obama-era regulations imposed on business and industry for environmental or labor-related reasons.

Top of the list are an eleventh-hour measure putting restrictions on mountaintop-removal coal mining due to take effect on 19 January, one day before Trump enters the White House, as well as rules obliging hydrocarbon industries to reduce methane emissions and reveal their payments to foreign governments for mining rights.

The Republicans are planning to employ an obscure tool to kill these directives off quickly. The Congressional Review Act allows them to block regulations within 60 legislative days after their issue with a simple majority in the Senate.

An additional target for repeal is the Dodd-Frank Financial Reform Act, which provides consumer protection viewed by Republicans as an undue burden on the financial sector.

Republican leaders have said that an overhaul of the tax code and a new infrastructure bill are also priorities, especially as they can claim some bipartisan support. Chuck Schumer, the new Democratic leader in the Senate, has expressed guarded backing for Trump’s stated ambitions for infrastructure renewal.

“We think it should be large. He’s mentioned a trillion dollars. I told him that sounded good to me,” Schumer told ABC News.

However, that backing is likely to melt away when it becomes clear how much of the program is based on tax breaks for corporations rather than government spending. Observers say that the promised restructuring of the tax code is also likely to be put on hold to make way for the GOP’s overwhelming priority, destroying Obamacare.

The one likely blossoming of bipartisanship in the early days of the new Congress will be the opening of an inquiry on Thursday by the Senate armed services committee into Russian hacking of the 2016 election. Democrats on the committee will join its chairman, Senator John McCain, and other Republican foreign policy hawks in seeking to focus the investigation on Moscow’s role in getting Trump elected.