Topeka ? In the span of one month, presumptive Republican presidential nominee John McCain’s lead in Kansas over Democrat Barack Obama has been cut in half, and Republican U.S. Sen. Pat Roberts’ margin over Democrat Jim Slattery also has dropped.

The GOP candidates still hold healthy leads over their rivals but the movement shown in the Rasmussen Reports released Monday was good news to Democrats.

Rasmussen Reports publishes public opinion polling information.

In the presidential race in Kansas, McCain led Obama in May, 55 percent to 34 percent, a 21-point edge.

But that fell to 47 percent to 37 percent in June, according to a telephone survey of 500 likely voters taken June 11. The survey, taken after Obama essentially clinched the Democratic nomination, has a margin of error of plus or minus 4 percentage points.

Rasmussen Reports has moved Kansas from “safely Republican” to “likely Republican” in the White House contest.

Kansas has not voted for a Democrat in a presidential race since supporting President Lyndon B. Johnson in 1964, and Christian Morgan, executive director of the state Republican Party, said Obama would not break the streak.

“There may be an interest in Obama right now, like looking at a car accident, but when it comes to voting for the next leader of the free world, I am confident Kansans will go with Senator McCain’s experience,” Morgan said.

In the Kansas U.S. Senate race, support for Roberts’ re-election has dropped 4 percentage points and slipped below 50 percent, according to the Rasmussen survey.

Roberts leads Slattery, a former congressman, 48 percent to 39 percent.

“Any incumbent who polls below 50 percent is considered potentially vulnerable,” the poll says.

In May, Roberts led Slattery 52 percent to 40 percent, according to the report.

“This race is in the competitive zone,” Slattery said. “I believe a true upset is in the making.”

Slattery faces Lee Jones, of Overland Park, in the Aug. 5 Democratic primary.

Again, the Kansas GOP said it was confident that Roberts would win.

“This is a long election,” Morgan said. “Kansans will vote for the leadership Senator Roberts provides, not the political expediency D.C. Jim provides.”