GOP residential candidate Scott Walker
Wisconsin Gov. Scott Walker speaks before an enthusiastic crowd at the 2012 Republican National ConventionReuters

Wealthy campaign contributors the Koch brothers have apparently picked their favorite Republican nominee: conservative Wisconsin Governor Scott Walker.

David Koch said at a Manhattan fundraiser for the New York State Republican Party that he and his brother, Charles, would support the party's nominee in the general election, but that it should be Walker, reported the New York Times.

Koch later said he was not officially endorsing anyone yet, though called Walker "terrific".

The apparent nod could be a massive boost for Walker's chances because the brothers plan to contribute as much as $900m (£600m) in campaign contributions until the next president is chosen in 2016.

Walker beat back a recall election in Wisconsin in 2012 with major support from the Koch brothers. The recall effort was launched after Walker slashed collective bargaining powers for state workers.

He represents the most conservative wing of the Republican Party and appears to be moving even further right as the campaign continues. He has said he would not support citizenship for illegal immigrants, is opposed to Obamacare, and is morally opposed to abortion.

A new CNN/ORR poll finds that Jeb Bush is leading the GOP pack among voters with 17% of Republicans and GOP-leaning independents backing him. Walker is close with 12%, but Rand Paul and Ted Cruz are hot on his heels with 11% supporting them.

In recent controversies Walker has commented that he "does not know" if President Obama is Christian, and has said he is capable of taking on ISIS because he has dealt with union protesters in Wisconsin.

In one of the most embarrassing gaffes which came to light during the campaign, Walker wrote "Molotov" in a letter to a Jewish constituent when he was Milwaukee County executive, apparently intending to say "Mazel Tov."