RICHMOND, VA - OCT 13: Democratic Sen. Mark R. Warner speaks during the debate with Republican challenger Ed Gillespie at the studios of WCVE in Richmond. 2014. (Timothy C. Wright/For the Washington Post)

EVERYONE ON Capitol Hill talks about the difficulty of getting big things done, and no wonder — there’s a pitifully short list of lawmakers who have made serious and sustained attempts at genuinely bipartisan solutions. Yet on any such list, Sen. Mark Warner of Virginia figures prominently. In taking on a range of key domestic challenges, he deserves reelection to a second term in the Senate.

As a freshman senator, Mr. Warner showed guts by defying large chunks of his Democratic base to support trimming entitlements such as Social Security and Medicare in order to forge a deal. By contrast, his Republican challenger, Ed Gillespie, a smart and savvy Washington insider, has promised never to compromise by backing new revenue in order to tackle the nation’s fiscal problems in a balanced way.

We understand that Mr. Gillespie, who faced a competitive GOP primary, is loath to alienate Republican hard-liners. Yet his opposition to any new taxes — read: any compromise — is exactly the sort of promise that produces congressional paralysis and would defeat a bargain to cure the nation’s fiscal ills.

Before he ran for the Senate in 2008, Mr. Warner was a highly successful governor whose signature success — a tax overhaul that preserved Virginia’s gold-plated credit rating and shored up its public schools — depended largely on his ability to cross partisan lines and attract substantial Republican support. In Washington, he has followed the same playbook.

His resolve to right America’s fiscal imbalance is based on pure pragmatism. As he has often noted, the urgency to ensure Social Security’s long-term viability by trimming benefits has nothing to do with ideology — just math. Or as Mr. Warner has put it: “Sixteen workers for every one retiree 50 years ago; three workers for every retiree now.”

Mr. Warner’s methods owe much to his attention to detail, a nearly obsessive search for creative solutions and real flexibility in long negotiating sessions, often over meals at his home. That, plus his Herculean drive, has earned him the respect of key Republican senators — and annoyed some of his party’s leaders.

Mr. Warner has distinguished himself in other ways — as a senator determined to crack big policy problems through bipartisan alchemy. He and Sen. Bob Corker (R-Tenn.) co-authored legislation that would reform the housing finance system by encouraging new firms to enter the mortgage securitization market; shield taxpayers from bailouts after big market dips; and shift more risks and rewards where they belong: with private investors.

Mr. Gillespie, a former lobbyist, national and state GOP chairman and top adviser to President George W. Bush, has deep political and policy experience. Unlike many Republicans who have been content to attack Obamacare, he proposed an alternative — albeit one that would offer far less protection to vulnerable patients.

Mr. Gillespie has the skills to be a bipartisan player in the Senate, as Mr. Warner has been. Yet by promising never to compromise on taxes, he has taken himself out of the hunt for an exit from America’s fiscal impasse. Virginians deserve better; in Mr. Warner, they have it.