Topeka ? Fresh off a closer-than-expected primary race, Gov. Sam Brownback on Wednesday held a victory party at the state Republican headquarters in Topeka, claiming credit for improving the economy and the state’s financial position.

But the celebration was quickly dampened with news that Standard & Poors, a leading credit rating agency, had just downgraded the state’s bond rating, due largely to the tax cuts and economic policies that Brownback has championed in his first term.

S&P announced Wednesday that it had lowered the state’s overall rating to AA, the third highest rating, from AA+. It also downgraded bonds that are backed by appropriations to AA- from AA.

“The downgrades reflect our view of a structurally unbalanced budget, following state income tax cuts that have not been matched with offsetting ongoing expenditure cuts in the fiscal 2015 budget,” S&P’s credit analyst David Hitchcock said in a news release.

“In our opinion, recent shortfalls in income taxes will leave both fiscal years 2014 and 2015 with ending general fund balances much less than projected in the enacted fiscal 2015 budget,” Hitchcock said.

Kansas ended fiscal year 2014 on June 30 with a general fund balance of $434.6 million, far short of the $687.4 million that had been projected.

The downgrade means Kansas could be forced to pay marginally higher interest rates on future bond issues.

The news came just as Brownback and other winners of Republican primaries gathered at the state GOP headquarters in Topeka to celebrate and kick off their general election campaigns.

During that rally, Brownback acknowledged State Treasurer Ron Estes, who was unopposed in his primary, and used the occasion to tout his own fiscal policy record.

“He (Estes) has had a little easier job,” Brownback said. “When he first came in we had less than a thousand bucks cash on hand at the end of that fiscal year. He had $434 million at the end of this last fiscal year we just had, so he’s got a little more money that he’s working with. The past team didn’t leave us with that.”

Brownback was referring to the state’s ending balance on June 30, 2010, six months before he and Estes took office. Revenues have recovered since then, but analysts attribute much of that to a temporary 1-cent sales tax increase passed by the 2010 Legislature at the urging of then-Gov. Mark Parkinson, a Democrat.

After criticizing that tax increase during his first campaign, Brownback later endorsed extending a portion of the sales tax increase while simultaneously backing historic cuts in state income taxes.

S&P is the second credit rating agency to downgrade Kansas since those income tax cuts were enacted. Moody’s Investors Services downgraded the state in May.

Democrat Paul Davis of Lawrence, who is challenging Brownback for re-election, was quick to react to the news.

“This is terrible news for Kansas and is further evidence that the governor’s economic experiment has failed,” Davis said in a statement. “This downgrade will cost Kansas even more money at a time when we can least afford it.”

Brownback said he disagrees with the rating analysts and defended his record on tax cuts.

“Breaking addictions to high taxes is hard,” he told reporters after the rally. “That’s a difficult thing to do.”

He also said investors who buy Kansas bonds should not be concerned about the state’s ability to repay them. “We will repay the bonds to investors. These are still high-grade bonds,” he said.

Brownback also said the tax cuts have stimulated the economy, noting that private-sector employment in Kansas is now at an all-time high.

According to data from the Bureau of Labor Statistics, however, private-sector job growth in Kansas has lagged behind most neighboring states, and the nation as a whole, since Brownback took office in January 2011.