Gov. Sam Brownback's election, in 2010, was supposed to be a harbinger of a conservative revolution in Kansas.

Brownback's uncompromising, ideological brand of politics marked a major departure from decades of moderate governors, Democratic and Republican; his supporters hailed his election as the beginning of a new political era for Kansas, foretelling a turn toward more conservative economic and social policies.

But, even then, his detractors warned that his election was not an open-ended mandate.

“Kansans want moderate leadership,” Tom Holland, Brownback's Democratic challenger, told The New York Times at the time. “We have a history again and again where conservatives take over and do something extreme and the voters kick them out of office.”

That might happen sooner than even Holland and Democrats could have predicted. Brownback has faced festering frustrations over some of his more aggressive policies, including tax cuts during a period of budget shortfalls in Kansas. This week, 100 Kansas Republicans cited this issue and others as they endorsed Brownback's Democratic opponent, Paul Davis, who has been keeping pace with Brownback in recent public polls.

Brownback's fragile political standing is especially significant because Kansas' political landscape so heavily favors Republicans. But Republicans are facing similar challenges in gubernatorial races elsewhere in the country.

After sweeping into 12 Democrat-held governors mansions in 2010, the GOP is now at risk of losing much of that ground in this election cycle. In Michigan, Ohio, Wisconsin, Pennsylvania, Florida and Maine -- the “most competitive” races for Republican incumbents, said RGA Executive Director Phil Cox on Wednesday -- Republican governors are either barely holding on in public polls or, in Pennsylvania and Maine, trailing significantly.

"These governors got elected on a very simple promise: that they would be moderate, non-ideological technocrat job creators," said Danny Kanner, a spokesman for the Democratic Governors Association. But they haven't delivered, Democrats say. "In all of these states the tax burden has been shifted from the very wealthy to the middle class and they haven't created the jobs they promised. … Working people in their states aren't feeling the recovery."

To a certain extent, it’s the political market self-correcting after the 2010 conservative wave. The Republican House candidates swept into office in that election cycle had their day of reckoning in 2012, when voters decided to send some of them back home. But this election cycle is the first major test for the gubernatorial class of 2010 — and the cracks are showing.

There are prominent counterexamples to the trend, including in New Mexico and Nevada, where Govs. Susana Martinez and Brian Sandoval, respectively, appear in strong positions to win re-election, despite being executives in states traditionally friendly to Democrats.

"Political waves can be overcome by good job performance,” said former RGA political director Josh Robinson, pointing to those races in particular.

But the mere size of the gubernatorial battleground for Republicans has serious, broader implications for the party.

As Congress has lain stagnant, Republicans have pointed to its governors as shining examples of the party's policies at work. Many GOP governors are also among the top-tier potential presidential candidates for 2016, including Scott Walker of Wisconsin and John Kasich of Ohio, both of whom are facing rigorous challenges this year. And, while Chris Christie has touted his fundraising successes as RGA chair, his ability to help his party's governors win may well determine whether he has a launching pad for a presidential bid in 2016.

In an otherwise strong political year for the GOP, when the party stands a chance at taking back its Senate majority, it is confounding to many Republicans to see their governors struggling with weak job approval ratings in traditional strongholds such as Kansas, Georgia and South Carolina.

The RGA has started to pump money into those states, and Cox said Wednesday that the RGA plans to spend $100 million in the final 100 days of the 2014 election in battleground governors races — roughly what Republicans spent on gubernatorial races during the whole of the 2010 election cycle.

This time, though, there seems a slimmer chance that Republicans will come out on top.