Republican state Sen. Ronnie Cromer fended off three challengers Tuesday to win re-election in a district where the majority of voters now live in a different county than Cromer.

Most people eligible to vote in the district reside in Lexington County, instead of Cromer’s home county of Newberry, because of recently redrawn district boundaries. And all of Cromer’s Republican primary challengers Tuesday were from Lexington County.

But Cromer campaigned heavily in the new territory, and the extra effort appeared to pay off when results of the GOP primary came in Tuesday night.

“We did as much as we could possibly do in trying to see everybody in Lexington County,’’ Cromer said after learning he had won.

Cromer defeated former television anchor Kara Gormley Meador, retired engineer Alan Hunter and one-time Lexington County GOP chairman Rich Bolen. He is virtually assured of retaining the Senate District 18 seat, because no Democrat filed to oppose him in the fall.

The race was one of four in the Midlands being watched closely.

In the Democratic primary to challenge incumbent Republican Sen. John Courson of Columbia, former sheriff’s Deputy Robert Rikard defeated Richland County Councilman Norman Jackson to run for the District 20 seat. Courson, president pro-tem of the Senate, is a moderate conservative who has shown strong support among voters in a district that often swings Democratic.

Sumter-area residents nominated attorney Thomas McElveen in the Democratic primary to replace retiring Sen. Phil Leventis, D-Sumter. McElveen will face either businessman Tony Barwick or lawyer Wade Kolb, who are in a runoff for the Republican nomination in District 35.

Aiken resident Deedee Vaughters took the Republican nomination for the right to face longtime Democratic Sen. Nikki Setzler in District 26. She defeated Duane Naquin of Lexington County. Setzler is a champion of education who has managed to hold his seat for years, even though his district is largely Republican. The district includes Lexington and Aiken counties.

Vaughters, a former board member with the conservative think tank the S.C. Policy Council, said voters are ready to elect a Republican.

“I did get some good news tonight,’’ she said. “I’m thrilled to be the Republican nominee.’’

Cromer’s re-election bid, however, was perhaps the most unusual Senate race locally because of the substantial changes in his district. Well over 50 percent of the district is now composed of Lexington County voters. During the campaign, the three challengers from Lexington County said voters needed a senator from their own county.

“I got beat up by my opponents for not living in Lexington County, but I live two miles from the county line on Lake Murray,’’ Cromer said. “I can see Lexington County across the lake.’’

A pharmacist from the Prosperity area, Cromer first won election to the state Senate nine years ago. The 64-year-old conservative, who is chairman of the Senate Wildlife Committee, replaced Andre Bauer as senator in 2003.