MARYLAND’S 6TH Congressional District, for years a Republican stronghold anchored by the state’s conservative far west, is suddenly the scene of a competitive race this fall, owing to a gerrymandered electoral map redrawn by Democrats in Annapolis.

The threat to the Republican incumbent, 86-year-old Roscoe Bartlett, who has represented the district for 20 years, is two-fold. First, the new boundaries encompass a chunk of western and northern Montgomery County, including Potomac, Gaithersburg, Germantown and Clarksburg, meaning an infusion of Democratic voters. Second, in open defiance of party chieftains who’d set the table for an insider, Democratic primary voters instead opted for John K. Delaney , a wealthy financier, to run against Mr. Bartlett.

As it happens, Mr. Delaney is an excellent candidate — shrewd, smart, hardworking and independent. He would be a standout representative for the 6th District and a marked improvement on Mr. Bartlett. We endorse Mr. Delaney.

In his 10 terms in office, the folksy Mr. Bartlett has not been the most dogmatic Republican on Capitol Hill. He was a relatively early champion of cutting America’s reliance on oil, rightly thinking it unsustainable. He opposed the detention of foreign fighters and terrorists at Guantanamo, based on the damage to America’s global image.

Yet on the fiscal and budgetary issues that have paralyzed Washington, Mr. Bartlett has marched in lockstep with his party’s most doctrinaire elements. He has been a champion of the tea party, refusing to raise taxes under any circumstances, opposing Obamacare and stimulus spending to jump-start the economy.

His opposition to public spending is often half-baked, as when he warned recently that it was a slippery slope from government-backed student loans to the Holocaust. He apologized, but it is just the sort of rhetoric, and thinking, that has made compromise so impossible in Congress.

He has been no more flexible on social issues, opposing same-sex marriage, sponsoring legislation that would outlaw abortion by defining “personhood” as beginning at conception, and opposing realistic reform of the nation’s broken immigration system.

By contrast, Mr. Delaney, an electrician’s son who has made a fortune in financial services, is a serious, business-minded pragmatist with a deep and broad understanding of the private sector, banking and job generation. That expertise, relatively rare for a Democrat, coupled with his experience as an executive, would give Mr. Delaney status and independence in Congress from the get-go.

Mr. Delaney is pro-choice. He favors marriage equality and the Dream Act, which would confer legal status on the children of undocumented immigrants who were brought to America at an early age. Also unlike Mr. Bartlett, he favors a balanced combination of fiscal reform — including higher taxes of capital gains — and spending cuts, including to entitlements, to tame the deficit.

Mr. Delaney is a newcomer to politics, but he is exceptionally well-versed in domestic issues. Moreover, he has the problem-solving skills to be an unusually effective congressman. Mr. Bartlett, after 20 years, is something very different: an ideologue who has become a part of the problem in Washington and in Congress.