“When you spend a lot of time talking about policy and debating policy in the presidential campaign, it is far easier to be specific about legislation when you get into office,” said Austan Goolsbee, who served as the chairman of the Council of Economic Advisers during the Obama administration. “President Trump spent the campaign fleshing out nothing in detail, so it’s not really a surprise that they can’t even agree on priorities, much less on actual legislative detail.”

House Republicans say slow and steady was always the plan. “We are 100 percent on pace with the 200-day plan we presented to President Trump and to members at our retreat,” Brendan Buck, a spokesman for Speaker Paul D. Ryan, wrote in an email. “Budget first (check), then regs (check), then Obamacare bill (in process and on schedule), and then tax (after Obamacare).”

But even Democrats, who had been gearing up for fights and compromises on health care, a tax overhaul, infrastructure and other policy matters, are bored and frustrated. “It’s painful for someone like me who was excited about infrastructure and tax reform,” said Representative Jim Himes, Democrat of Connecticut. “It seems like the administration and the majority are nowhere.”

Congressional Republicans seem wary of offering their own bills, lest Mr. Trump or one of his aides, who have largely been distracted by personnel and intelligence scandals, undercut their efforts. This was most visible when Mr. Trump demanded that Republicans come up with a replacement plan for a health care law they had hoped to simply repeal, sending members flailing. The administration also gave conflicting messages on a tax plan embraced by House Republicans that would apply the corporate tax rate to all imports while exempting exports.

“On our side, it’s pretty clear who drives policy,” said a Republican aide who spoke on the condition of anonymity to avoid being written about by Mr. Trump on Twitter. “But take any issue and try to figure that out from their side.”

Is the leading influence Mr. Trump’s policy adviser, Stephen Miller, who presents himself as the voice of the White House? Or the president’s son-in-law, Jared Kushner? Or Vice President Mike Pence? No one seems to know.