Tea party and conservative groups have been sustaining challenger Milton Wolf in the final days of his campaign to unseat U.S. Sen. Pat Roberts in the Kansas Republican primary.

Roberts told a radio interviewer Monday that Wolf can’t win the November general election.

The election is Tuesday, and both Roberts and Wolf had campaign events Monday in the Kansas City suburbs of Johnson County. It is the state’s most populous county and a GOP stronghold.

Finance reports show that over the past week, three conservative groups have spent $219,000 on mailings and television ads to boost Wolf’s campaign.

But Roberts said told Topeka radio’s WIBW “NewsNow at Noon” that voting for Wolf is voting to elect a Democrat to the U.S. Senate in November.

Wolf’s campaign dismissed the claim.