Like you, I am studying candidates for president - and have found out some amazing things. On the Republican side, there is quite a pile of dirt - damaging history, criminal behavior, and so on. Relatively little of it is being made public. If I could find it, so can Hillary and the Democrats, and they will use it when it is most useful to them.
Until there is a clear Republican front runner, it makes sense for the Democrats to sit on the dirt. They want a vulnerable opponent. The Republicans have the opposite problem. If they bring up dirt they are accused of fighting a dirty campaign and harming someone who could be a front runner later. Reagan's admonition about speaking ill of a Republican still has some effect.
Thus the dirt in the Republican candidates' past and present is a ticking time bomb waiting for a clear front runner. For now, the only bombs that the Democrats are launching are against each other. They have already tried to destroy each other in a race and gender war.
The Hillary style "fun" is just beginning. Thus the fireworks are in full blast on the Democrat side, but still relatively dormant on the Republican side.
Not all Republican candidates are alike. Some have an amazing amount of dirty baggage, while others are relatively clean. Take for example a relatively clean candidate, Ron Paul. I have supported Ron Paul for many years because he supports free markets and the Constitution. He has been the Jiminy Cricket of the Congress, pointing out the unconstitutionality of many things while the Congressional nose has kept growing. Still he does have some problems that the public is kept relatively unaware of:
Ron Paul has a major conflict of interest between his political priorities and his private investments. According to his financial disclosure sheets for the last two available years , he has amassed large scale holdings of numerous gold companies while at the same time advocating a return to the gold standard and trashing the dollar. 
If a Democrat had amassed holdings in a pharmaceutical company and then advocated policies that would drive up the price of drugs, we would call it a conflict of interest. If George Bush held oil company stock and then urged oil prices to rise, there would be an outcry. Ron Paul's position is logically no different.
Ron Paul even explicitly blamed the Treasury Dept. of keeping the price of gold down when much of his personal assets were likely in gold, and tried to use his position in Congress to stop the alleged price suppression:
"Congressman Ron Paul: There's a strong suspicion that our government, in the Treasury department and specifically Exchange Stabilization Fund are probably dealing in the gold market with the purpose of keeping the price of gold down. They deny this and maybe they're getting around it some way. But I wanted to make it explicit that they can't do it, that it's illegal, because the interpretation of the law passed in the 1930s did give the Exchange Stabilization Fund some authority to deal in gold. But I want to change that. And I want it to be out in the open. And I want Congress to know about it, if they're going to loan gold or sell gold. They claim they're not doing it, but if that's the case, the Treasury shouldn't have any objections to a law like this, that just says that Congress is just resuming their responsibilities that they should have had, and should have had never taken away from them." 
Ron Paul is (or recently was) also a partner in a company called Carr Ltd. Carr Ltd. has been very hard to find out about. For a company in business it is very quiet: it has no listed phone number or internet presence. It may be a partnership with Daniel Carr the coin designer. Daniel Carr is most famous for his gold Amero coins  and he shares Ron Paul's politics.  Ron Paul is also reported to have owned a coin company at some time between his stints in Congress. 
Ron Paul also owns (or recently owned) Carona Limited, a real estate company. Real estate and Carona in Texas suggests (but does not prove) a connection to John Carona. John Carona is a Texas businessman and legislator who is a major player in the real estate and property management world. He has pushed legislation that would create multiple new toll roads with 30 year leases, and legislation that would force neighborhoods to form homeowner associations that would in turn benefit his business dealings and/or potentially be compelled to pay fees.  The Carona plan is reminiscent of the Supreme Court's disastrous Kelo decision. If Ron Paul has real estate dealings with Carona, it is likely legal, but somewhat unsavory.
I presume you already know about the racist content of the Ron Paul newsletters that were made public by former supporters.  In addition, Ron Paul has been against and publicly blamed the Civil War on Lincoln even though several states had succeeded before he was even president.  In his mind, states rights trumped slavery problems and the Civil War was just a means for Lincoln to destroy states rights.
He also has been in the habit of putting earmarks in bills for constituents, and then voting against the bill, secure in the knowledge that it would pass without his vote.  Thus he got the political benefits of earmarks while being able to say he never voted for any earmarks. That might bother some people after his talk about being off the public dole.
You may also have heard about the amusing endorsements of Ron Paul by a famous brothel owner  and and the f-bombed endorsement by Howard Stern  . You may have also have heard of the wealthy Google donations. "Where the extreme left and the extreme right meet, you'll find Ron Paul," said Merle Black, an Emory University political scientist.  His largest contributor group is Google. 
You might have heard that a Muslim newspaper endorsed him and urged its readers to vote in the Michigan primary because of his position against the war on Islamic terrorism.  You probably have not heard about his sponsoring a bill to allow the commercial cultivation of hemp in 2007.  He is in favor of legalizing marijuana. While these things may not bother some people, it probably does bother others who may be supporting him.
Part of the reason why Ron Paul is raising so much money is because he is given a pass by most of the Leftist mainstream media. Only in the debates have his less marketable positions come through to the public. The media are not covering the more embarrassing or alienating aspects of Ron Paul. They want him in the race.
Remember how Ross Perot split the Conservative vote and gave the election to Bill Clinton? Clinton won even though he didn't have a majority. McCain and the media are hoping Ron Paul will similarly split the Conservatives, and thus deliver the primary to a Liberal Republican like McCain. Ron Paul does not have the votes to win a primary, but he does have the votes to lose it for the Conservatives. Thus the Leftist donations and media assistance come to him.
Ron Paul is earnest and mostly consistent over the years. America has needed its Jiminy Cricket of the Constitution. However, he is not as perfect as the mainstream media or his supporters would like us all to believe for their own political purposes.
We could accidentally end up with a liberal Republican candidate RINO even if we Conservatives have a majority. It might be McCain, or it could even be a another Arkansas governor Bill Clinton clone from Hope. Are we destined to repeat history in our primary? Our opponents are counting on it.
I expect to hear a lot of complaints from the supporters of Ron Paul. Trying to tell a supporter about a candidate's problems is like telling a young lover about problems with his fiance. They don't want to hear it and they don't want you to hear it. Nevertheless, word needs to get out now. Waiting only plays into Hillary's hands.
2. http://www.opensecrets.org/pfds/pfd2006/N00005906_2006.pdf http://www.opensecrets.org/pfds/pfd2005/N00005906_2005.pdf
17. http://www.votehemp.com/paul_floor_comments_2.html http://www.austinchronicle.com/gyrobase/Issue/column?oid=oid:477963