Yes, Donald Trump should be investigated so that the extent of his ties to Russia can be determined. It has recently been discovered that a reputable source with experience in Russia has let American officials know that Russia has compromising video of Donald Trump and that Mr. Trump is a Russian plant.
There is nothing wrong with investigating potential ties between President-elect Trump and Russia. However, an investigation does not mean that Trump is actually guilty of any wrongdoing. The Obama Administration was often investigated by Congressional Republicans who the Democrats charged as just being on a witch hunt. Now the shoe is on the other foot for Democrats calling on Congressional investigations.
The allegations against Trump are very serious and should not be taken lightly. Already, he has shown that he is willing to side with Russia against his own intelligence agencies. As president, he should be above reproach. There's an old saying that "where there's smoke, there's fire." It seems to me that there is a lot of smoke around this issue.
Knowing exactly what the ties are between Trump and the Russian government is extremely important to the safety and security of our nation. I think it needs to be investigated, so that we can feel confident in our future. If it is found that there is a major conflict of interest, we need and deserve to know.