The President is the only person who is elected by all of the people in this country and can reasonably lay claim to any kind of national mandate.....because of what has happened over the years regarding how congress is elected and who its members represent. The House of Representatives was supposed to represent the will of all the people as it was originally envisioned.....but it has been gerrymandered to such an extent that such a claim no longer holds any real meaning. The proof of that was in the 2012 House elections when The Democrats won a total of 1.4 million more votes from the people....but the Republicans won something like 33 more seats. How in hell does that represent the "will of the people"? And, of course, the Senate can in no way claim to represent the "will of the people" when you have a situation where California & Wyoming are each represented by two members in its body.
So, therein lies the problem. We need checks & balances, of course, but we need to somehow make the congress more representative of all the people if it is to have any fair claim to deserve equal power with a president who was elected by every voter in the country. And right now, any idea that Congress fairly reflects the will of the American people on a "one person, one vote" basis is totally unfounded.