According to Wheeler, what role did the sinking of the Maine play in causing the war?

In General Wheelers own words, "this terrible catastrophe [sinking of the Maine] though not the cause of the outbreak of hostilities, certainly hastened the action of Congress in its declaration of war against Spain." According to Wheeler the Spains actions in Cuba were already leading to war between Spain and the US. The sinking of the Maine was the final straw that decided the congress to vote for war. But war would have come without the sinking of the Maine.