A statewide poll conducted by the Paul Simon Public Policy Institute shows Republican Sen. Mark Kirk and Democratic Rep. Tammy Duckworth are early frontrunners in the race for incumbent Kirk’s U.S. Senate seat. 

Both candidates polled at above 50 percent of surveyed registered voters who are likely to vote in the upcoming primary election on March 15. Duckworth is contesting the Senate seat held by Kirk, who has been subject of recent criticisms from within his own party.

“These results provide just a snapshot of public opinion in Illinois at this juncture, but it is a good indicator of where the races stand with three weeks to go before the race,” John Jackson, a visiting professor who helped design the poll, said in a press release.

Kirk was the pick for 53 percent of registered Republican survey respondents who are likely to vote in the primary. His Republican challenger James Marter, a conservative Oswego businessman, polled at 14 percent. One third of the total 306 Republican registered voters were undecided. The reported margin of error for the Republican sample was plus or minus 5.6 percentage points.

Although the poll indicated a strong lead for Kirk to win the primary, 39 percent of respondents approve of the job he is doing and 31 percent disapprove. An “unusually larger number” — 25 percent — of voters did not know whether he was performing well in his duties as a senator, Jackson said. 

“This is probably indicative of why he is being challenged by his own party,” he said.

MORE: Obama Supreme Court nominee should get hearing, Kirk says

Comparatively, Democratic Sen. Dick Durbin, who won re-election in 2014 and has four years left in his term, received a 51 percent job-approval rating and a 34 percent disapproval rating. 

Duckworth is leading the three-way contest for the seat, winning 52 percent of surveyed Democrats. Andrea Zopp, head of the Chicago Urban League, and State Sen. Napoleon Harris, D-Harvey, trailed Duckworth, garnering 6 and 4 percent, respectively. 

There were 422 registered voters who said they would vote in the Democratic primary of the 1,000 surveyed, and the poll shows a margin of error of plus or minus 4.7 percentage points.

Jackson said Kirk and Duckworth were widely considered to be the leading candidates for the party nominations. 

“So far they are living up to those expectations,” he said.

Bill Lukitsch can be reached at [email protected] or (618) 536-3329.