WASHINGTON — For the billionaires, the multimillionaires and the plain well-off people whom President-elect Donald J. Trump is choosing for his cabinet, the first step to office will be the sort of grilling he didn’t face — on potential business conflicts of interest and, for some, tax returns — courtesy of the Senate sleuths who have taken their toll in the past.

President Obama’s first Treasury secretary, Timothy F. Geithner, was nearly derailed in 2009. His first choice for secretary of health and human services, Tom Daschle, did not make it through that year.

Now the billionaires Betsy DeVos, Linda McMahon and Wilbur L. Ross Jr., and the multimillionaires Rex W. Tillerson, Ben Carson, Elaine Chao, Steven Mnuchin, Representative Tom Price, Andrew F. Puzder and Todd Ricketts can expect much of the same scrutiny.

“With the president-elect flouting a 40-year bipartisan tradition of disclosure and transparency, we think it’s more important than ever to ensure that senior officials across government aren’t operating under a different tax code than everyone else,” warned Senator Ron Wyden of Oregon, the senior Democrat on the Senate Finance Committee, which has upended its share of nominees.