(WHTM) – The Republican race for Pennsylvania’s U.S. Senate seat continues to tighten with three candidates polling in double digits in a new Franklin & Marshall College poll.

The poll of 357 registered Republican Pennsylvania voters has Mehmet Oz with 18%, Dave McCormick with 16%, and Kathy Barnette with 12%.

Carla Sands finished with 5%, Jeff Bartos received 2%, and Joe Gale received 1% support. George Bochetto had 0% support and 5% said they supported another candidate.

Voters remain largely undecided with 39% still unsure of who they’ll vote for on May 17.

Favorability ratings of Oz remain negative among Republican voters, with the former television personality having more of an unfavorable (41%) than favorable (29%) opinion.

McCormick has more positive (31%) than negative (17%) favorability ratings than Oz, but 38% of Republicans say they don’t know enough about McCormick to have an opinion.

Oz (19%) and Barnette (18%) are running neck and neck among the Trump faction of Republican voters, while McCormick (28%) has an advantage among the traditional faction.

Former President Trump endorsed Oz in the crowded race early last month.

Among Republicans who voted in the May 2018 primary election, McCormick (20%) and Oz (18%) are also essentially tied.

The interviews were conducted at the Center for Opinion Research at Franklin & Marshall. The data included in this release represent the responses of 792 registered Pennsylvania voters, including 357 Democrats, 325 Republicans, and 110 independents.

The sample error for this survey is +/- 4.4 percentage points when the design effects from weighting are considered.