With less than a week before election day, Donald Trump is widening his lead in Oklahoma's Republican primary race, according to a poll released Wednesday.

The real estate mogul is holding an eight-point lead over Florida Sen. Marco Rubio, with 29 percent to Rubio's 21 percent, according to the poll. That lead has widened from just 5 percent two weeks ago.

Meanwhile, Rubio has overtaken Texas Sen. Ted Cruz, who was in second place two weeks ago with 25 percent. Cruz polled at 20 percent in this week's poll.

Retired neurosurgeon Ben Carson came in fourth, with 6 percent, and Ohio Gov. John Kasich was fifth, with 5 percent. Another 18 percent told pollsters they remained undecided, and 2 percent said they planned to vote for another candidate.