DOVER — Delaware Republican Party Chairman Mike Harrington Sr. announced Tuesday he will not seek a second term in the position.

Mr. Harrington, elected as chairman in 2017, revealed the information in an email to Republicans.

"At the Lincoln Day dinner in Kent County a few weeks ago, I announced that I would run again for Chairman to lead the 2020 fight," he wrote. "I fully understood that it would again be a difficult job but I had signed up for the long haul. I was prepared to fulfill that commitment.

"I had some ideas to improve our efforts from the experiences of 2018 and despite the odds, believed we could do better in 2020 with the President as top of the ticket. Unfortunately, a number of personal matters have stepped in the way.

"They are items that I cannot postpone. They will monopolize my time. I can’t give the time and commitment that I know from experience is required to do the job as your Chairman. So reluctantly I must step away."

The 2018 election was a disastrous one for Delaware Republicans. Although both chambers of the General Assembly and the governor’s office have been controlled by the Democratic Party since the 2008 election, the Democratic edge in the Senate was just 11-10 heading into November.

With several Democratic senators retiring and with the attorney general’s post open, Republicans felt they had a chance to shift the balance of power in the state.

Instead, they went backward.

Two of the top Republican legislators, Senate Minority Whip (and presumed caucus leader with Minority Leader Gary Simpson retiring) Greg Lavelle and House Minority Whip Deborah Hudson, were defeated. Democrats also took out Treasurer Ken Simpler, who was seeking a second term, and won the auditor’s office, which was being vacated by Republican Tom Wagner after 30 years.

Voters also elected Democrats for attorney general, U.S. senator and U.S. representative, giving the party control of all nine statewide seats for the first time since the 1800s.

"Despite the best efforts of everyone—State Committee—Regional Committees –individual candidates —2018 was not a good year. While we had some local successes, losing our two Republican statewide offices to the Blue Wave really hurts," Mr. Harrington wrote.

"Could we have done some thing’s (sic) differently? Sure, but the overwhelming numbers is the real story."

He attributed the Republican defeat to simple math: Although a higher percentage of Republicans cast ballots in 2018 (58 percent compared to 55 percent of Democrats), the GOP could not compete with the Democratic Party’s registration advantage, as Democratic voters outnumbered Republican ones about 180,000 to 113,000.

"Frankly, there is nothing else all of us could have done," Mr. Harrington wrote.

Mr. Simpler made similar comments after the election.

"I think the Republican Party is going to have to do some soul-searching to figure out how, if it can’t overcome the registration deficit materially, how do you at least message to people that your brand is distinguishable from what’s happening at the national level, because clearly independents and Democratic voters came out in this election cycle and were registering dissatisfaction with things that went beyond Delaware," he said.

"And Republicans facing the registration deficit, I think it’s going to be very challenging for a new candidate to message through that unless there is some thoughtful position that resonates with those independents and soft Democrat voters."

The GOP also had egg on its face last year when Scott Walker won the Republican primary for the party’s nomination for the House. Mr. Walker, who ran for the same seat as a Democrat in 2016 and is viewed in political circles as somewhat of a joke, was formally denounced and shunned by the Republican Party after a series of bizarre and inflammatory Facebook posts.

Despite those setbacks, Mr. Harrington believes the GOP made progress in a number of areas in 2018, engaging new voters, raising funds and spreading information about its candidates. For 2020, he wrote, the party should "establish a social media campaign in those targeted districts (even before we have candidates) on issues and voting records where the incumbents are out-of-step with" constituents.

The party will pick a new leader at its state convention May 4.

Chuck Boyce, who was pursuing the GOP nomination for the Senate before dropping out due to health issues last year, announced in February he would seek the chairmanship.

A voicemail left for Mr. Harrington Tuesday was not returned.