Sen. Larry Craig (R.-Idaho) has had good career in Washington, spending more than 27 years in Congress with stints in both the House and Senate. But with news of Craig’s arrest, under highly suspicious circumstances nonetheless, now would be a good time bid farewell to Washington. With a re-election campaign looming next year, it seems he has little other choice.

Craig has been a solid conservative, compiling a 93% lifetime rating from the American Conservative Union. The few times I’ve had an opportunity to interview him, he’s always been an articulate spokesman for Senate Republicans. And while I didn’t agree with his support for comprehensive immigration reform or opening up trade with Cuba — citing the need boost Idaho’s agriculture industry — there were few other issues where he strayed from traditional conservative issues.

Unfortunately for Craig, rumors about past homosexual conduct, combined with tonight’s embarrassing arrest report, leave him little choice but to step down — either immediately or at the end of his term. RedState’s Erick Erickson put it bluntly: “I can only say he must resign.” And Hugh Hewitt said “an immediate exit is required.”

Should Craig leave immediately — which I doubt will happen — he would most likely be replaced by Idaho Lt. Gov. Jim Risch, according to liberal blog Daily Kos, which has surprising good information about the potential Senate race. (Patrick Ruffini has also compiled a list of possible replacements.)

Coming in the wake of Sen. David Vitter’s adultery and former Rep. Mark Foley’s transgressions, this news further tarnishes congressional Republicans. How very sad for a party that once stood for moral values.

UPDATE — Aug. 28, 9:12 a.m.: Chris Cillizza of The Fix has a good report about Craig’s political future and who might replace him in Idaho.