The retirement of Sen. Barbara Mikulski at a time when Maryland voters are rallying around Republican Gov. Larry Hogan gives the state's minority party the best chance it has had in a generation to capture one of the state's two U.S. Senate seats. When Republican primary voters go to the polls Tuesday, they should pick the candidate not only best positioned to take advantage of that opportunity but also to serve the state with distinction in Washington, and that is attorney Chrys Kefalas.

Mr. Kefalas is just 36, but he has a tremendous resume of experience that prepares him to succeed in the Senate. He served as deputy legal counsel under Republican Gov. Robert L. Ehrlich Jr., handling hundreds of executive clemency requests (as well as helping to defend the administration from a Democratic investigation of hiring and firing practices). He worked for the U.S. Department of Justice under Attorney General Eric Holder to foster the growing bipartisan consensus around criminal justice reform. He is on leave now from the National Association of Manufacturers, a job that has provided him key insights into what needs to be done to retain and create good-paying jobs for American workers. And his roots in his family business — Costa's Inn, arguably the best crab joint in Baltimore — give him the retail politicking and customer service skills that Ms. Mikulski has trained Maryland voters to expect.

He faces tough competition from Del. Kathy Szeliga, who represents Baltimore and Harford counties and serves as minority whip, and Richard Douglas, an Iraq veteran and attorney who has experience both in the George W. Bush administration and on Capitol Hill. Ms. Szeliga is an appealing politician who is well liked on both sides of the aisle in Annapolis, and her experience as a small-business owner gives her an important perspective. Mr. Douglas has a particularly strong base of knowledge on foreign policy issues, and he is the only candidate in the Republican primary to have run for statewide office before. He ran a close second to Dan Bongino in the 2012 Senate primary, garnering nearly 60,000 votes.

But the breadth and depth of Mr. Kefalas' knowledge of the issues stood out. He is well versed in the details of legislative debates on taxes, immigration, trade and the economy, and he takes positions that make sense for Maryland. He understands, for example, the importance of well-constructed international trade deals for the Port of Baltimore — and in turn for Maryland's economy. He understands the frustration of a middle class that feels the deck is stacked against them and proposes steps to simplify the tax code without exploding the federal deficit. He is appropriately cautious about committing U.S. troops abroad, and he understands the need to reverse the devastating effect the war on drugs has had in places like Baltimore.

Mr. Kefalas refers to himself as a Larry Hogan Republican, and the influence of the governor, with whom he worked closely during the Ehrlich administration, shines through. Just like Mr. Hogan, Mr. Kefalas focuses on the economic issues that unite many of Maryland's Democrats and Republicans, not the social issues that divide them. It's never easy for a Republican to win a statewide election here, but the bruising Democratic Senate primary and contrarian mood among voters gives the party a real shot this year.

Ms. Mikulski was first elected to the Senate in 1986 after the retirement of Maryland's last Republican senator, Charles M. “Mac” Mathias. If the state's Republicans want their best chance to reclaim the seat, they should vote for Chrys Kefalas on Tuesday.