The story behind Mr. Pompeo’s meeting with Raytheon, which has not been previously reported, is emblematic of the outsize influence wielded in Washington by Mr. Urban and a small group of other lobbyists and operatives who backed Mr. Trump when most of the K Street establishment was keeping its distance. Those relationships became lucrative after Mr. Trump won a surprise victory on Election Day and rewarded early loyalists with key posts, continued access or both.

With Mr. Trump lagging in the polls, the lobbyists are seeking to protect that mutually beneficial relationship by working to re-elect him, underscoring the mix of politics and policy that has served them — and their clients — so well over the last three and a half years.

Consider the examples of eight lobbyists and operatives with ties to lobbying firms, including Mr. Urban, who are now assisting Mr. Trump’s campaign in various paid and unpaid capacities, like fund-raising and strategy.