Rep. James Lankford (R-Okla.) has a lead over former Oklahoma Speaker T.W. Shannon (R) going into Tuesday's Senate primary election, but the race could be headed for an August runoff, according to a new poll.
The few public polls of the race haven't offered a clear picture of its state of play, though most have shown it to be competitive. An earlier SoonerPoll in May found the race in a dead heat, while an internal poll for Lankford released in May found him with a 10-point lead and a late April poll for a pro-Shannon outside group found him with a 10-point lead.
Lankford came into the race with much more money to spend, but Shannon has benefitted from support from some national conservative groups.
The SoonerPoll of 840 likely Republican primary voters, surveyed on landlines and cell phones, was conducted from June 19-21 and has a margin of error of plus or minus 3.38 percentage points.