Why do Republicans lie about our President so often?

because the truth isn't good, for Republicans

The truth isn't good for liberals either, now is it?

The truth is just fine, for Democrats.  The Republicans cannot run on the truth. If Republicans were truthful they would have to admit that BUSH broke the economy and spent us into the poor house and that republicans have stood in the way of any executive or legislative action that might aide us in recovery because they needed our fiscal house to remain the total mess they made of it under Bush in order to blame their failures on President Obama in the upcoming election.

Republican leaders have made no secret about their agenda.  Since day one of The Presidents term in office Republican leaders have stated but one goal, to defeat Obama and for almost 4 years THAT is all they have focused on. 

for almost 4 years we have watched as republicans have become less and less rooted in reality, we have endured endless demands for Obama's Birth Certificate, his college grades, his proof he is an America. we have endured endless obstruction in congress, record filibusters, insulting language, racist inuendos, and all manner of attacks on the President, his family, his loyalty et al.  The President has met every attack with grace that even Jackie Robinson would marvel at while continuing to move our country forward from the mess the Republicans created. 

THIS is the truth that Republicans cannot run on, admit or even face and this is why they LIE so much.

The following quote by Roosevelt should apply to every president, regardless of which political party they belong to. And even though I didn't care much for Bush. I always tried to be truthful. And even though I like Obama. I still fact check accusations made against him. And to be brutally honest. Most of the time those accusations are unfounded.

"The President is merely the most important among a large number of public servants. He should be supported or opposed exactly to the degree which is warranted by his good conduct or bad conduct, his efficiency or inefficiency in rendering loyal, able, and disinterested service to the Nation as a whole. Therefore it is absolutely necessary that there should be full liberty to tell the truth about his acts, and this means that it is exactly necessary to blame him when he does wrong as to praise him when he does right. Any other attitude in an American citizen is both base and servile. To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public. Nothing but the truth should be spoken about him or any one else. But it is even more important to tell the truth, pleasant or unpleasant, about him than about any one else."