Richard Painter, who served as an ethics attorney in the George W. Bush administration (2005-2007) said the following:
The facts now in this investigation are much worse than the facts in the early stages of Watergate, which was a simple break-in ordered by midlevel campaign officials — not by the president. Here we have facts that are much worse: We have a foreign power that has orchestrated a break-in. It’s a much worse situation than the outset of Watergate.
Even worse than Watergate? That's pretty bad, since Watergate was the blackest mark on our presidency in our history. But I think he may be right. And it's just beginning. I have a feeling that, like Watergate, much worse things will be revealed in the future.
Watergate was bad. It involved the president, in an effort to cover up the misdeeds of his underlings, breaking the law and lying to the American people in an effort to hold on to power. But it's looking like the Trump scandal involves a candidate colluding with a foreign power, an enemy of this country, to seize power by subverting the electoral process. That's not just illegal, but it borders on (if not actually reaching) the level of treason.
There must be an investigation to find out the whole truth regarding this mess. And congressional Republicans just make themselves look bad by trying to block a full investigation. The American people have the right to know what happened.