In recent days, the transition focus has been on President-elect Donald Trump’s retreat from some high-profile campaign stances and his personnel choices, including some unseemly public infighting over whether former critic Mitt Romney should be secretary of state.

But the more important aspect of the transition for Trump’s long-term success may be the extent to which his team and congressional Republicans can craft viable legislative proposals to implement the policy changes he promised would spur economic growth and “make America great again.”

Trump himself signaled in his revised 100-day agenda that he realizes this may prove harder than his sweeping campaign rhetoric suggested. He stressed using his executive authority to spur energy production and crack down on visa violators and excluded such high-profile promises as repealing and replacing Obamacare, building a wall to stop illegal immigration from Mexico and enacting a massive job-creating $1 trillion infrastructure upgrade program.

In each area, Trump could confront significant differences with congressional Republicans, who developed their own legislative proposals in hopes of having a GOP president to help enact them.

Potentially contentious areas include:

• Infrastructure. It’s crucial to Trump’s hope of creating millions of new jobs and spurring economic growth. But Republican lawmakers are expressing concern about the cost, reflecting their long-held belief that new spending programs should be totally funded.

Senate Democrats like the idea better but plan to fight a rumored version that would finance some $1 trillion in upgrades to roads, bridges, tunnels and airports with tax credits designed to encourage contractors to undertake needed projects. Some Republicans would prefer to confine new tax breaks to a tax reform bill.

Ron Klain, a former top aide to President Barack Obama and Vice President Joe Biden, warned Democrats in The Washington Post that Trump’s tax credit proposal was a “trap” to get support for “a tax-cut plan for utility-industry and construction-sector investors, and a massive corporate welfare plan for contractors” because there was no guarantee it would fund any new projects.

Another possibility is some version of Hillary Clinton’s campaign promise for an infrastructure bank designed to attract private investment for new projects.

• Obamacare. Trump pledged to ask Congress on Day 1 “to immediately deliver a full repeal of Obamacare.” GOP lawmakers are chomping at the bit, having voted some 60 times in recent years to repeal the landmark Affordable Care Act.

Selecting Rep. Tom Price as secretary of health and human services puts a strong voice for repeal in the Cabinet. But Trump complicated matters when he told The Wall Street Journal he might keep popular but costly provisions requiring insurers to cover those with pre-existing conditions and let parents cover their children until age 26. That raises the question of helping insurance companies pay their costs if the program’s revenue-raising sections are killed.

Senate Democrats, meanwhile, say they’ll fight any effort to scrap Obamacare and, with 48 votes, may be able to force a compromise on replacing it. Some Republican governors are reportedly concerned about the political impact of depriving 22 million constituents of their newly acquired health care. Adding to the potentially politically incendiary mix, Price backs fellow House Republicans trying to partially privatize Medicare, a program Trump said he’d protect.

The outcome is murky, but lawmakers might end up revising the ACA over a two- or three-year period, rather than eliminating it.

• Immigration. Trump’s repeated promise to build “a great wall” to block immigration and make Mexico pay the tab may find favor in neither Congress nor Mexico.

And in a post-election interview on CBS’ “60 Minutes,” Trump seemed to back off building a wall that is “impenetrable, physical, tall, powerful,” noting “there could be some fencing” in what might become a less dramatic expansion of the current combination of physical and electronic barriers along the 1,989-mile U.S.-Mexico border.

• Tax reform. This remains the likeliest area for action within Trump’s first six months because congressional Republicans have already done substantial work on possible legislation. Most pending proposals would simplify the current tax laws and reduce taxes for all, with the biggest breaks going to corporations and the wealthiest taxpayers.

But some analysts fear the revenue loss from Trump’s tax plan would balloon the deficit, even using “dynamic scoring” by which GOP sponsors can claim that economic growth will offset most of it.

Trump vowed to increase annual economic growth, below 2.5 percent for the past decade, to 4 percent, a level not achieved since the 1997-1999 dotcom boom. And he promised to create 25 million new jobs, setting a clear target to measure his success.

— Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News.