Alabama’s electoral calendar makes the question that has loomed for eight months — How well will Mr. Jones’s success transfer to other Democrats? — especially stark, particularly in a state that has tilted almost entirely toward Republicans in recent years.

“There’s got to be a stemming of that tide, before you can say that his election was a high-water mark that stopped the Republicans from winning,” John H. Merrill, the Republican secretary of state, said in his Capitol office.

Republicans have plenty of reasons for confidence despite the Senate setback. For one thing, none of the major Republican candidates running this year are as perennially controversial or, at this point, as politically radioactive as Roy S. Moore, the former State Supreme Court chief justice who won the party’s nomination in the Senate race, only to see his campaign collapse after he was accused of sexual misconduct. For another, Alabama’s most powerful Democrats are far from united; there have been open clashes, including an attempt this month by Mr. Jones to oust the state party chairwoman.

Most of all, there are the numbers: More than twice as many voters cast ballots in the Republican primary for governor as in the Democratic primary. Studies consistently rank Alabama among the nation’s most conservative states, and among the least elastic, meaning there are relatively few swing voters. And even against an opponent who had become a pariah, Mr. Jones won by just 21,924 votes out of more than 1.3 million cast.

Mr. Jones acknowledges that his victory was “not in and of itself indicative of a long-term trend.” But he and other Democrats say it laid a foundation for them to mount competitive campaigns in certain races this year, including some for statewide office.